diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc1.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc1.ts
index f57c1a8101bd6..80c8f168b865a 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc1.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc1.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @Filename: test123.ts
 /////** @type {number} */
 ////var [|x|];
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc10.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc10.ts
index 98cc31e32075b..ba5fb3ecfdbb6 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc10.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc10.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 /////**
 //// * @param {?} x
 //// * @returns {number}
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc11.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc11.ts
index a08906ef91a19..6a59fa45a467b 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc11.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc11.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 /////**
 //// * @param {?} x
 //// * @returns {number}
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc12.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc12.ts
index ec1ab37022214..d7a73c3f35091 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc12.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc12.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////class C {
 ////    /**
 ////     * @return {...*}
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc17.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc17.ts
index c452dd4516f20..f2cb9b9ded395 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc17.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc17.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 ////class C {
 ////    /**
 ////     * @param {number} x - the first parameter
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc18.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc18.ts
index 9fc2e966028aa..043ff1d043053 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc18.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc18.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 ////class C {
 ////    /** @param {number} value */
 ////    set c(value) { return value }
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc3.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc3.ts
index f7d0522018abd..de7bc34e174e6 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc3.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc3.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 /////**
 //// * @param {number} x - the first parameter
 //// * @param {{ a: string, b: Date }} y - the most complex parameter
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc6.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc6.ts
index dbb75590fb2ba..8e384be0f32d3 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc6.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc6.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////declare class C {
 ////    /** @type {number | null} */
 ////    p;
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc7.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc7.ts
index 0d43bde45d49b..f9ce9f7a15265 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc7.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc7.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 /////**
 //// * @param {number} x
 //// * @returns {number}
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc8.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc8.ts
index ca9450c1e6ff0..cbc6ca33cdd9a 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc8.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc8.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 /////**
 //// * @param {number} x
 //// * @returns {number}
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc9.5.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc9.5.ts
index aa17b0591c85d..a7196ef0e411e 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc9.5.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc9.5.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 /////**
 //// * @template T
 //// * @param {T} x
diff --git a/tests/cases/fourslash/annotateWithTypeFromJSDoc9.ts b/tests/cases/fourslash/annotateWithTypeFromJSDoc9.ts
index f664d5be6b7b8..138bb3f27561e 100644
--- a/tests/cases/fourslash/annotateWithTypeFromJSDoc9.ts
+++ b/tests/cases/fourslash/annotateWithTypeFromJSDoc9.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 /////**
 //// * @param {?} x
 //// * @returns {number}
diff --git a/tests/cases/fourslash/cloduleAsBaseClass.ts b/tests/cases/fourslash/cloduleAsBaseClass.ts
index 9de78e58cce82..fab294793393f 100644
--- a/tests/cases/fourslash/cloduleAsBaseClass.ts
+++ b/tests/cases/fourslash/cloduleAsBaseClass.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////class A {
 ////    constructor(x: number) { }
 ////    foo() { }
diff --git a/tests/cases/fourslash/cloduleAsBaseClass2.ts b/tests/cases/fourslash/cloduleAsBaseClass2.ts
index c628a0f859a2d..e517d1049642d 100644
--- a/tests/cases/fourslash/cloduleAsBaseClass2.ts
+++ b/tests/cases/fourslash/cloduleAsBaseClass2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 // @Filename: cloduleAsBaseClass2_0.ts
 ////class A {
 ////    constructor(x: number) { }
diff --git a/tests/cases/fourslash/cloduleTypeOf1.ts b/tests/cases/fourslash/cloduleTypeOf1.ts
index 6d57ff2f45c5a..b7ce305b68086 100644
--- a/tests/cases/fourslash/cloduleTypeOf1.ts
+++ b/tests/cases/fourslash/cloduleTypeOf1.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////class C<T> {
 ////    static foo(x: number) { }
 ////    x: T;
diff --git a/tests/cases/fourslash/codeFixAddMissingAsync2.ts b/tests/cases/fourslash/codeFixAddMissingAsync2.ts
index 3f610ae141bbd..aaadea94be5a9 100644
--- a/tests/cases/fourslash/codeFixAddMissingAsync2.ts
+++ b/tests/cases/fourslash/codeFixAddMissingAsync2.ts
@@ -1,4 +1,5 @@
 /// <reference path="fourslash.ts" />
+// @strict: false
 ////interface Stuff {
 ////    b: () => Promise<string>;
 ////}
diff --git a/tests/cases/fourslash/codeFixAddMissingDeclareProperty.ts b/tests/cases/fourslash/codeFixAddMissingDeclareProperty.ts
index e4ebea338f6c3..3fbf486511756 100644
--- a/tests/cases/fourslash/codeFixAddMissingDeclareProperty.ts
+++ b/tests/cases/fourslash/codeFixAddMissingDeclareProperty.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 // @useDefineForClassFields: true
 
 ////class B {
diff --git a/tests/cases/fourslash/codeFixAddMissingEnumMember12.ts b/tests/cases/fourslash/codeFixAddMissingEnumMember12.ts
index af813c71f7f5b..4935e1323288d 100644
--- a/tests/cases/fourslash/codeFixAddMissingEnumMember12.ts
+++ b/tests/cases/fourslash/codeFixAddMissingEnumMember12.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////const x; // this is x
 ////
 ////// this is E
diff --git a/tests/cases/fourslash/codeFixAddMissingProperties1.ts b/tests/cases/fourslash/codeFixAddMissingProperties1.ts
index 0d82892c02ca1..ee9cb81160251 100644
--- a/tests/cases/fourslash/codeFixAddMissingProperties1.ts
+++ b/tests/cases/fourslash/codeFixAddMissingProperties1.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////interface Foo {
 ////    a: number;
 ////    b: string;
diff --git a/tests/cases/fourslash/codeFixAddMissingProperties33.ts b/tests/cases/fourslash/codeFixAddMissingProperties33.ts
index c034471a4205a..4ada2d89fdc54 100644
--- a/tests/cases/fourslash/codeFixAddMissingProperties33.ts
+++ b/tests/cases/fourslash/codeFixAddMissingProperties33.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 ////interface Foo {
 ////    a: number;
 ////    b: string;
diff --git a/tests/cases/fourslash/codeFixAddMissingProperties37.ts b/tests/cases/fourslash/codeFixAddMissingProperties37.ts
index cdc0b7e82f775..9811e04e93324 100644
--- a/tests/cases/fourslash/codeFixAddMissingProperties37.ts
+++ b/tests/cases/fourslash/codeFixAddMissingProperties37.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////interface I {
 ////    x: number;
 ////    y: number;
diff --git a/tests/cases/fourslash/codeFixAddMissingProperties43.ts b/tests/cases/fourslash/codeFixAddMissingProperties43.ts
index bf50ec73974c9..086ef47fb0f25 100644
--- a/tests/cases/fourslash/codeFixAddMissingProperties43.ts
+++ b/tests/cases/fourslash/codeFixAddMissingProperties43.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////interface Foo {
 ////    a: number;
 ////    b: string;
diff --git a/tests/cases/fourslash/codeFixAddMissingProperties44.ts b/tests/cases/fourslash/codeFixAddMissingProperties44.ts
index 5cb87bd2a53d9..f648912e8ab40 100644
--- a/tests/cases/fourslash/codeFixAddMissingProperties44.ts
+++ b/tests/cases/fourslash/codeFixAddMissingProperties44.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 // @lib: es2020
 // @target: es2020
 
diff --git a/tests/cases/fourslash/codeFixAddMissingProperties6.ts b/tests/cases/fourslash/codeFixAddMissingProperties6.ts
index d4d4e2eb8dd98..b042ba5aa1970 100644
--- a/tests/cases/fourslash/codeFixAddMissingProperties6.ts
+++ b/tests/cases/fourslash/codeFixAddMissingProperties6.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////interface I {
 ////    x: number;
 ////    y: number;
diff --git a/tests/cases/fourslash/codeFixAwaitInSyncFunction6.5.ts b/tests/cases/fourslash/codeFixAwaitInSyncFunction6.5.ts
index b33d50078ef19..99d54ddd95a53 100644
--- a/tests/cases/fourslash/codeFixAwaitInSyncFunction6.5.ts
+++ b/tests/cases/fourslash/codeFixAwaitInSyncFunction6.5.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////const f = promise => {
 ////    await promise;
 ////}
diff --git a/tests/cases/fourslash/codeFixAwaitInSyncFunction6.ts b/tests/cases/fourslash/codeFixAwaitInSyncFunction6.ts
index 5fc50a4f9d7f5..314edcc3ce63d 100644
--- a/tests/cases/fourslash/codeFixAwaitInSyncFunction6.ts
+++ b/tests/cases/fourslash/codeFixAwaitInSyncFunction6.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////const f = (promise) => {
 ////    await promise;
 ////}
diff --git a/tests/cases/fourslash/codeFixCannotFindModule_suggestion.ts b/tests/cases/fourslash/codeFixCannotFindModule_suggestion.ts
index 83e17f170ba0e..205a1c9a84f02 100644
--- a/tests/cases/fourslash/codeFixCannotFindModule_suggestion.ts
+++ b/tests/cases/fourslash/codeFixCannotFindModule_suggestion.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @moduleResolution: bundler
 // @Filename: /node_modules/abs/subModule.js
 ////export const x = 0;
diff --git a/tests/cases/fourslash/codeFixChangeJSDocSyntax15.ts b/tests/cases/fourslash/codeFixChangeJSDocSyntax15.ts
index 748eae2716189..832e8df3926a7 100644
--- a/tests/cases/fourslash/codeFixChangeJSDocSyntax15.ts
+++ b/tests/cases/fourslash/codeFixChangeJSDocSyntax15.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 //// var f = <[|function(number?): number|]>(x => x);
 
 verify.codeFix({
diff --git a/tests/cases/fourslash/codeFixClassExtendAbstractSomePropertiesPresent.ts b/tests/cases/fourslash/codeFixClassExtendAbstractSomePropertiesPresent.ts
index 0a9df34bc8851..b127cfefda22e 100644
--- a/tests/cases/fourslash/codeFixClassExtendAbstractSomePropertiesPresent.ts
+++ b/tests/cases/fourslash/codeFixClassExtendAbstractSomePropertiesPresent.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitOverride: true
 //// abstract class A {
 ////    abstract x: number;
diff --git a/tests/cases/fourslash/codeFixClassImplementClassMemberAnonymousClass.ts b/tests/cases/fourslash/codeFixClassImplementClassMemberAnonymousClass.ts
index ee8b8cafffeae..84b9236c94847 100644
--- a/tests/cases/fourslash/codeFixClassImplementClassMemberAnonymousClass.ts
+++ b/tests/cases/fourslash/codeFixClassImplementClassMemberAnonymousClass.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// class A {
 ////     foo() {
 ////         return class { x: number; }
diff --git a/tests/cases/fourslash/codeFixClassImplementClassPropertyModifiers.ts b/tests/cases/fourslash/codeFixClassImplementClassPropertyModifiers.ts
index 9614213798fb8..d20c3302b5e55 100644
--- a/tests/cases/fourslash/codeFixClassImplementClassPropertyModifiers.ts
+++ b/tests/cases/fourslash/codeFixClassImplementClassPropertyModifiers.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////abstract class A {
 ////    abstract x: number;
 ////    private y: number;
diff --git a/tests/cases/fourslash/codeFixClassImplementClassPropertyTypeQuery.ts b/tests/cases/fourslash/codeFixClassImplementClassPropertyTypeQuery.ts
index 3c34de1e1bf61..fe2f291c2b654 100644
--- a/tests/cases/fourslash/codeFixClassImplementClassPropertyTypeQuery.ts
+++ b/tests/cases/fourslash/codeFixClassImplementClassPropertyTypeQuery.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////class A {
 ////    A: typeof A;
 ////}
diff --git a/tests/cases/fourslash/codeFixClassImplementDeepInheritance.ts b/tests/cases/fourslash/codeFixClassImplementDeepInheritance.ts
index c9a568effbf8a..1f01ea708c271 100644
--- a/tests/cases/fourslash/codeFixClassImplementDeepInheritance.ts
+++ b/tests/cases/fourslash/codeFixClassImplementDeepInheritance.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////// Referenced throughout the inheritance chain.
 ////interface I0 { a: number }
 ////
diff --git a/tests/cases/fourslash/codeFixClassImplementInterfaceComputedPropertyNameWellKnownSymbols.ts b/tests/cases/fourslash/codeFixClassImplementInterfaceComputedPropertyNameWellKnownSymbols.ts
index 371d6115b14bb..f9eebb3e727d8 100644
--- a/tests/cases/fourslash/codeFixClassImplementInterfaceComputedPropertyNameWellKnownSymbols.ts
+++ b/tests/cases/fourslash/codeFixClassImplementInterfaceComputedPropertyNameWellKnownSymbols.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @lib: es2017
 
 ////interface I<Species> {
diff --git a/tests/cases/fourslash/codeFixClassImplementInterfaceDuplicateMember2.ts b/tests/cases/fourslash/codeFixClassImplementInterfaceDuplicateMember2.ts
index 9b4831e07024d..0058806179c39 100644
--- a/tests/cases/fourslash/codeFixClassImplementInterfaceDuplicateMember2.ts
+++ b/tests/cases/fourslash/codeFixClassImplementInterfaceDuplicateMember2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// interface I1 {
 ////     x: number;
 //// }
diff --git a/tests/cases/fourslash/codeFixClassImplementInterfaceHeritageClauseAlreadyHaveMember.ts b/tests/cases/fourslash/codeFixClassImplementInterfaceHeritageClauseAlreadyHaveMember.ts
index b67bd966f9ea0..6c9923b62a3be 100644
--- a/tests/cases/fourslash/codeFixClassImplementInterfaceHeritageClauseAlreadyHaveMember.ts
+++ b/tests/cases/fourslash/codeFixClassImplementInterfaceHeritageClauseAlreadyHaveMember.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// class Base {
 ////     foo: number;
 //// }
diff --git a/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplements1.ts b/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplements1.ts
index 13d58d0ad6e9b..0be3862475738 100644
--- a/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplements1.ts
+++ b/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplements1.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// interface I1 {
 ////     x: number;
 //// }
diff --git a/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplements2.ts b/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplements2.ts
index 946b6495c5f98..517ce22074043 100644
--- a/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplements2.ts
+++ b/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplements2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// interface I1 {
 ////     x: number;
 //// }
diff --git a/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplementsIntersection2.ts b/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplementsIntersection2.ts
index e43c44063e634..8b7bb55705aee 100644
--- a/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplementsIntersection2.ts
+++ b/tests/cases/fourslash/codeFixClassImplementInterfaceMultipleImplementsIntersection2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// interface I1 {
 ////     x: number;
 //// }
diff --git a/tests/cases/fourslash/codeFixClassImplementInterfaceOptionalProperty.ts b/tests/cases/fourslash/codeFixClassImplementInterfaceOptionalProperty.ts
index 9cb6f47773329..6c2b7717f381d 100644
--- a/tests/cases/fourslash/codeFixClassImplementInterfaceOptionalProperty.ts
+++ b/tests/cases/fourslash/codeFixClassImplementInterfaceOptionalProperty.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////interface IPerson {
 ////    name: string;
 ////    birthday?: string;
diff --git a/tests/cases/fourslash/codeFixClassImplementInterfaceSomePropertiesPresent.ts b/tests/cases/fourslash/codeFixClassImplementInterfaceSomePropertiesPresent.ts
index 4b61ea41e40b7..2b93b0e4a78e9 100644
--- a/tests/cases/fourslash/codeFixClassImplementInterfaceSomePropertiesPresent.ts
+++ b/tests/cases/fourslash/codeFixClassImplementInterfaceSomePropertiesPresent.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////
 //// interface I {
 ////     x: number;
diff --git a/tests/cases/fourslash/codeFixCorrectReturnValue10.ts b/tests/cases/fourslash/codeFixCorrectReturnValue10.ts
index 61523d804b1a7..89ab1a6b9be15 100644
--- a/tests/cases/fourslash/codeFixCorrectReturnValue10.ts
+++ b/tests/cases/fourslash/codeFixCorrectReturnValue10.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// const a: ((() => number) | (() => undefined)) = () => { 1 }
 
 verify.codeFixAvailable([
diff --git a/tests/cases/fourslash/codeFixCorrectReturnValue18.ts b/tests/cases/fourslash/codeFixCorrectReturnValue18.ts
index a5f7eca4c1ab0..3e911df6577b0 100644
--- a/tests/cases/fourslash/codeFixCorrectReturnValue18.ts
+++ b/tests/cases/fourslash/codeFixCorrectReturnValue18.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //@Filename: file.tsx
 //// declare namespace JSX {
 ////     interface Element { }
diff --git a/tests/cases/fourslash/codeFixCorrectReturnValue19.ts b/tests/cases/fourslash/codeFixCorrectReturnValue19.ts
index 4b13495bac63e..3bda538a4f50d 100644
--- a/tests/cases/fourslash/codeFixCorrectReturnValue19.ts
+++ b/tests/cases/fourslash/codeFixCorrectReturnValue19.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //@Filename: file.tsx
 //// declare namespace JSX {
 ////     interface Element { }
diff --git a/tests/cases/fourslash/codeFixCorrectReturnValue20.ts b/tests/cases/fourslash/codeFixCorrectReturnValue20.ts
index 81072badec043..fa654e987af30 100644
--- a/tests/cases/fourslash/codeFixCorrectReturnValue20.ts
+++ b/tests/cases/fourslash/codeFixCorrectReturnValue20.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //@Filename: file.tsx
 //// declare namespace JSX {
 ////     interface Element { }
diff --git a/tests/cases/fourslash/codeFixCorrectReturnValue8.ts b/tests/cases/fourslash/codeFixCorrectReturnValue8.ts
index 640f84af4d047..b1ff11eedb3c5 100644
--- a/tests/cases/fourslash/codeFixCorrectReturnValue8.ts
+++ b/tests/cases/fourslash/codeFixCorrectReturnValue8.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// function Foo (a: (() => number) | (() => undefined) ) { a() }
 //// Foo(() => { 1 })
 
diff --git a/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile6.ts b/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile6.ts
index 952628c6cac89..7db7808c46e38 100644
--- a/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile6.ts
+++ b/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile6.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowjs: true
 // @noEmit: true
 // @checkJs: true
diff --git a/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile7.ts b/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile7.ts
index 11f027d4f35b9..b68de9267e672 100644
--- a/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile7.ts
+++ b/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile7.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowjs: true
 // @noEmit: true
 // @checkJs: true
diff --git a/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile8.ts b/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile8.ts
index 334b275c87771..5f20a9502aed9 100644
--- a/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile8.ts
+++ b/tests/cases/fourslash/codeFixDisableJsDiagnosticsInFile8.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowjs: true
 // @noEmit: true
 // @checkJs: true
diff --git a/tests/cases/fourslash/codeFixForgottenThisPropertyAccess01.ts b/tests/cases/fourslash/codeFixForgottenThisPropertyAccess01.ts
index 22ca176aa032d..5f0dddaabcf8d 100644
--- a/tests/cases/fourslash/codeFixForgottenThisPropertyAccess01.ts
+++ b/tests/cases/fourslash/codeFixForgottenThisPropertyAccess01.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @Filename: /a.ts
 ////export const foo = 0;
 
diff --git a/tests/cases/fourslash/codeFixForgottenThisPropertyAccess02.ts b/tests/cases/fourslash/codeFixForgottenThisPropertyAccess02.ts
index 6f6c6f5510d41..ec019c348b8d0 100644
--- a/tests/cases/fourslash/codeFixForgottenThisPropertyAccess02.ts
+++ b/tests/cases/fourslash/codeFixForgottenThisPropertyAccess02.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////class C {
 ////    constructor(public foo) {
 ////    }
diff --git a/tests/cases/fourslash/codeFixForgottenThisPropertyAccess03.ts b/tests/cases/fourslash/codeFixForgottenThisPropertyAccess03.ts
index 2dd1c47b6f7a3..52b7c7faa66e0 100644
--- a/tests/cases/fourslash/codeFixForgottenThisPropertyAccess03.ts
+++ b/tests/cases/fourslash/codeFixForgottenThisPropertyAccess03.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////class C {
 ////    foo: number;
 ////    constructor() {[|
diff --git a/tests/cases/fourslash/codeFixInferFromUsageConstructor.ts b/tests/cases/fourslash/codeFixInferFromUsageConstructor.ts
index aa74fb2f6ffb2..d9a7e062ebc00 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageConstructor.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageConstructor.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 // @strictNullChecks: true
 
 ////class TokenType {
diff --git a/tests/cases/fourslash/codeFixInferFromUsageConstructorFunctionJS.ts b/tests/cases/fourslash/codeFixInferFromUsageConstructorFunctionJS.ts
index 2177e5b8ea03c..894d34fa18535 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageConstructorFunctionJS.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageConstructorFunctionJS.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 // @allowJs: true
 // @checkJs: true
 // @noImplicitAny: true
diff --git a/tests/cases/fourslash/codeFixInferFromUsageGetter2.ts b/tests/cases/fourslash/codeFixInferFromUsageGetter2.ts
index a50d471ad12d3..38649188bd316 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageGetter2.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageGetter2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitAny: true
 ////class C {
 ////    [|get x() |]{
diff --git a/tests/cases/fourslash/codeFixInferFromUsageInaccessibleTypes.ts b/tests/cases/fourslash/codeFixInferFromUsageInaccessibleTypes.ts
index 91dfcffafc0d8..10687392cce2e 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageInaccessibleTypes.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageInaccessibleTypes.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitAny: true
 ////function f1(a) { a; }
 ////function h1() {
diff --git a/tests/cases/fourslash/codeFixInferFromUsageOptionalParam.ts b/tests/cases/fourslash/codeFixInferFromUsageOptionalParam.ts
index f9b7277e4cc73..3796cdd1efcf8 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageOptionalParam.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageOptionalParam.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitAny: true
 ////function f([|a? |]){
 ////    a;
diff --git a/tests/cases/fourslash/codeFixInferFromUsageOptionalParamJS.ts b/tests/cases/fourslash/codeFixInferFromUsageOptionalParamJS.ts
index dbf29fe2f5d4e..d18b35aedf54b 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageOptionalParamJS.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageOptionalParamJS.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowJs: true
 // @checkJs: true
 // @noImplicitAny: true
diff --git a/tests/cases/fourslash/codeFixInferFromUsageRestParam.ts b/tests/cases/fourslash/codeFixInferFromUsageRestParam.ts
index b4713181d9ad9..b4179fb15b59f 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageRestParam.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageRestParam.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitAny: true
 ////function f(a: number, [|...rest |]){
 ////    a; rest;
diff --git a/tests/cases/fourslash/codeFixInferFromUsageRestParam2.ts b/tests/cases/fourslash/codeFixInferFromUsageRestParam2.ts
index 0b0d0e1dfbfa9..15fd04c6271d1 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageRestParam2.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageRestParam2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitAny: true
 ////function f(a: number, [|...rest |]){
 ////    a; rest;
diff --git a/tests/cases/fourslash/codeFixInferFromUsageRestParam2JS.ts b/tests/cases/fourslash/codeFixInferFromUsageRestParam2JS.ts
index d5c1fd54bb59a..1b3e36430a4f2 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageRestParam2JS.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageRestParam2JS.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowJs: true
 // @checkJs: true
 // @noImplicitAny: true
diff --git a/tests/cases/fourslash/codeFixInferFromUsageRestParamJS.ts b/tests/cases/fourslash/codeFixInferFromUsageRestParamJS.ts
index 4b7f046ca18af..d6086ebf6dbbe 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageRestParamJS.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageRestParamJS.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowJs: true
 // @checkJs: true
 // @noImplicitAny: true
diff --git a/tests/cases/fourslash/codeFixInferFromUsageString.ts b/tests/cases/fourslash/codeFixInferFromUsageString.ts
index d58998cf4a31a..a6c66af0511ce 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageString.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageString.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitAny: true
 //// function foo([|p, a, b |]) {
 ////     var x
diff --git a/tests/cases/fourslash/codeFixInitializePrivatePropertyJS.ts b/tests/cases/fourslash/codeFixInitializePrivatePropertyJS.ts
index 1b991d06a1c5c..b61be3d567329 100644
--- a/tests/cases/fourslash/codeFixInitializePrivatePropertyJS.ts
+++ b/tests/cases/fourslash/codeFixInitializePrivatePropertyJS.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowjs: true
 // @checkJs: true
 
diff --git a/tests/cases/fourslash/codeFixMissingTypeAnnotationOnExports28-long-types.ts b/tests/cases/fourslash/codeFixMissingTypeAnnotationOnExports28-long-types.ts
index 1de6a9ea124d7..a3ef35e5ff4a0 100644
--- a/tests/cases/fourslash/codeFixMissingTypeAnnotationOnExports28-long-types.ts
+++ b/tests/cases/fourslash/codeFixMissingTypeAnnotationOnExports28-long-types.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 // @isolatedDeclarations: true
 // @declaration: true
 // fileName: code.ts
diff --git a/tests/cases/fourslash/codeFixOverrideModifier10.ts b/tests/cases/fourslash/codeFixOverrideModifier10.ts
index 362fd859608bc..0e2af30da7024 100644
--- a/tests/cases/fourslash/codeFixOverrideModifier10.ts
+++ b/tests/cases/fourslash/codeFixOverrideModifier10.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitOverride: true
 
 //// class B {
diff --git a/tests/cases/fourslash/codeFixOverrideModifier9.ts b/tests/cases/fourslash/codeFixOverrideModifier9.ts
index 0361a75e52fe2..4b581dd1f4787 100644
--- a/tests/cases/fourslash/codeFixOverrideModifier9.ts
+++ b/tests/cases/fourslash/codeFixOverrideModifier9.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitOverride: true
 
 //// class B {
diff --git a/tests/cases/fourslash/codeFixOverrideModifier_js1.ts b/tests/cases/fourslash/codeFixOverrideModifier_js1.ts
index 8f3584021cb92..bd8c4f4876d01 100644
--- a/tests/cases/fourslash/codeFixOverrideModifier_js1.ts
+++ b/tests/cases/fourslash/codeFixOverrideModifier_js1.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 // @allowJs: true
 // @checkJs: true
 // @noEmit: true
diff --git a/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS1.ts b/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS1.ts
index ccc7c97115026..f880c469aa01a 100644
--- a/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS1.ts
+++ b/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS1.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowJs: true
 // @checkJs: true
 // @filename: /a.js
diff --git a/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS2.ts b/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS2.ts
index 89acd2ff5904f..02f14bf1b447c 100644
--- a/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS2.ts
+++ b/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowJs: true
 // @checkJs: true
 // @filename: /a.js
diff --git a/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS3.ts b/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS3.ts
index 13c11a224c9b9..f1f97a0e70d47 100644
--- a/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS3.ts
+++ b/tests/cases/fourslash/codeFixRenameUnmatchedParameterJS3.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @allowJs: true
 // @checkJs: true
 // @filename: /a.js
diff --git a/tests/cases/fourslash/codeFixSpellingVsMissingMember.ts b/tests/cases/fourslash/codeFixSpellingVsMissingMember.ts
index 71fd41d5c7c01..5352f4b4a9599 100644
--- a/tests/cases/fourslash/codeFixSpellingVsMissingMember.ts
+++ b/tests/cases/fourslash/codeFixSpellingVsMissingMember.ts
@@ -2,6 +2,7 @@
 
 // Tests that the spelling fix is returned first.
 
+// @strict: false
 ////class C {
 ////    foof: number;
 ////    method() {
diff --git a/tests/cases/fourslash/codeFixUndeclaredAcrossFiles1.ts b/tests/cases/fourslash/codeFixUndeclaredAcrossFiles1.ts
index a8171668751d2..73f72c499d15c 100644
--- a/tests/cases/fourslash/codeFixUndeclaredAcrossFiles1.ts
+++ b/tests/cases/fourslash/codeFixUndeclaredAcrossFiles1.ts
@@ -1,4 +1,5 @@
 /// <reference path='fourslash.ts' />
+// @strict: false
 // @allowJs: true
 // @checkJs: true
 
diff --git a/tests/cases/fourslash/codeFixUndeclaredClassInstance.ts b/tests/cases/fourslash/codeFixUndeclaredClassInstance.ts
index 024ec144092c8..a432861ae5d6d 100644
--- a/tests/cases/fourslash/codeFixUndeclaredClassInstance.ts
+++ b/tests/cases/fourslash/codeFixUndeclaredClassInstance.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// class A {
 ////     a: number;
 ////     b: string;
diff --git a/tests/cases/fourslash/codeFixUndeclaredClassInstanceWithTypeParams.ts b/tests/cases/fourslash/codeFixUndeclaredClassInstanceWithTypeParams.ts
index 34e359feea89f..9711ad9b959a8 100644
--- a/tests/cases/fourslash/codeFixUndeclaredClassInstanceWithTypeParams.ts
+++ b/tests/cases/fourslash/codeFixUndeclaredClassInstanceWithTypeParams.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// class A<T> {
 ////     a: number;
 ////     b: string;
diff --git a/tests/cases/fourslash/codeFixUndeclaredPropertyFunctionEmptyClass.ts b/tests/cases/fourslash/codeFixUndeclaredPropertyFunctionEmptyClass.ts
index 6f0a5de3557b1..1bf54f8fc213b 100644
--- a/tests/cases/fourslash/codeFixUndeclaredPropertyFunctionEmptyClass.ts
+++ b/tests/cases/fourslash/codeFixUndeclaredPropertyFunctionEmptyClass.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// [|class A {
 ////     constructor() {
 ////         this.x = function(x: number, y?: A){
diff --git a/tests/cases/fourslash/codeFixUndeclaredPropertyFunctionNonEmptyClass.ts b/tests/cases/fourslash/codeFixUndeclaredPropertyFunctionNonEmptyClass.ts
index 30d7e13cb56cb..acda34621165b 100644
--- a/tests/cases/fourslash/codeFixUndeclaredPropertyFunctionNonEmptyClass.ts
+++ b/tests/cases/fourslash/codeFixUndeclaredPropertyFunctionNonEmptyClass.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// [|class A {
 ////     y: number;
 ////     constructor(public a: number) {
diff --git a/tests/cases/fourslash/codeFixUndeclaredPropertyObjectLiteral.ts b/tests/cases/fourslash/codeFixUndeclaredPropertyObjectLiteral.ts
index a2647c5a21e33..8eec6c164f6f0 100644
--- a/tests/cases/fourslash/codeFixUndeclaredPropertyObjectLiteral.ts
+++ b/tests/cases/fourslash/codeFixUndeclaredPropertyObjectLiteral.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// [|class A {
 ////     constructor() {
 ////         let e: any = 10;
diff --git a/tests/cases/fourslash/codeFixUnusedIdentifier_deleteWrite2.ts b/tests/cases/fourslash/codeFixUnusedIdentifier_deleteWrite2.ts
index 2fe01399355a0..8723e1e4a16b4 100644
--- a/tests/cases/fourslash/codeFixUnusedIdentifier_deleteWrite2.ts
+++ b/tests/cases/fourslash/codeFixUnusedIdentifier_deleteWrite2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noLib: true
 // @noUnusedLocals: true
 
diff --git a/tests/cases/fourslash/codeFixUnusedIdentifier_prefix.ts b/tests/cases/fourslash/codeFixUnusedIdentifier_prefix.ts
index 80b2b9bb75ceb..55b4e00a1c404 100644
--- a/tests/cases/fourslash/codeFixUnusedIdentifier_prefix.ts
+++ b/tests/cases/fourslash/codeFixUnusedIdentifier_prefix.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noUnusedLocals: true
 // @noUnusedParameters: true
 
diff --git a/tests/cases/fourslash/codeFixUnusedIdentifier_suggestion.ts b/tests/cases/fourslash/codeFixUnusedIdentifier_suggestion.ts
index 19e06e0616593..08574d2d655ed 100644
--- a/tests/cases/fourslash/codeFixUnusedIdentifier_suggestion.ts
+++ b/tests/cases/fourslash/codeFixUnusedIdentifier_suggestion.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 ////function f([|p|]) {
 ////    const [|x|] = 0;
 ////}
diff --git a/tests/cases/fourslash/codefixInferFromUsageNullish.ts b/tests/cases/fourslash/codefixInferFromUsageNullish.ts
index d1073a9d9a958..66a2f04264f5f 100644
--- a/tests/cases/fourslash/codefixInferFromUsageNullish.ts
+++ b/tests/cases/fourslash/codefixInferFromUsageNullish.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noImplicitAny: true
 ////declare const a: string
 ////function wat([|b |]) {
diff --git a/tests/cases/fourslash/completionCloneQuestionToken.ts b/tests/cases/fourslash/completionCloneQuestionToken.ts
index 67df1cabb4a90..71ea89081b436 100644
--- a/tests/cases/fourslash/completionCloneQuestionToken.ts
+++ b/tests/cases/fourslash/completionCloneQuestionToken.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 // @Filename: /file2.ts
 //// type TCallback<T = any> = (options: T) => any;
 //// type InKeyOf<E> = { [K in keyof E]?: TCallback<E[K]>; };
diff --git a/tests/cases/fourslash/completionListsThroughTransitiveBaseClasses.ts b/tests/cases/fourslash/completionListsThroughTransitiveBaseClasses.ts
index f4fd276502807..0d63653b93f43 100644
--- a/tests/cases/fourslash/completionListsThroughTransitiveBaseClasses.ts
+++ b/tests/cases/fourslash/completionListsThroughTransitiveBaseClasses.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////declare class A {
 ////    static foo;
 ////}
diff --git a/tests/cases/fourslash/completionListsThroughTransitiveBaseClasses2.ts b/tests/cases/fourslash/completionListsThroughTransitiveBaseClasses2.ts
index 5adade8c2a70b..035f030a4819d 100644
--- a/tests/cases/fourslash/completionListsThroughTransitiveBaseClasses2.ts
+++ b/tests/cases/fourslash/completionListsThroughTransitiveBaseClasses2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////declare class A {
 ////    foo;
 ////}
diff --git a/tests/cases/fourslash/completionsOverridingMethod9.ts b/tests/cases/fourslash/completionsOverridingMethod9.ts
index 5026f3aa8aac6..d99f1bd0a7adf 100644
--- a/tests/cases/fourslash/completionsOverridingMethod9.ts
+++ b/tests/cases/fourslash/completionsOverridingMethod9.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 // @Filename: a.ts
 // @newline: LF
 
diff --git a/tests/cases/fourslash/consistentContextualTypeErrorsAfterEdits.ts b/tests/cases/fourslash/consistentContextualTypeErrorsAfterEdits.ts
index 27feb9eac590d..a6f980133f535 100644
--- a/tests/cases/fourslash/consistentContextualTypeErrorsAfterEdits.ts
+++ b/tests/cases/fourslash/consistentContextualTypeErrorsAfterEdits.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 //// class A {
 ////     foo: string;
 //// }
diff --git a/tests/cases/fourslash/constEnumsEmitOutputInMultipleFiles.ts b/tests/cases/fourslash/constEnumsEmitOutputInMultipleFiles.ts
index 6cf29e8b6fedc..f0d8c10462af7 100644
--- a/tests/cases/fourslash/constEnumsEmitOutputInMultipleFiles.ts
+++ b/tests/cases/fourslash/constEnumsEmitOutputInMultipleFiles.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 // @Filename: a.ts
 // @newLine: lf
 ////const enum TestEnum {
diff --git a/tests/cases/fourslash/contextualTypingOfArrayLiterals.ts b/tests/cases/fourslash/contextualTypingOfArrayLiterals.ts
index 7318eeee6cb33..1a553e52f7669 100644
--- a/tests/cases/fourslash/contextualTypingOfArrayLiterals.ts
+++ b/tests/cases/fourslash/contextualTypingOfArrayLiterals.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////class C {
 ////    name: string;
 ////    age: number;
diff --git a/tests/cases/fourslash/defaultParamsAndContextualTypes.ts b/tests/cases/fourslash/defaultParamsAndContextualTypes.ts
index b5e05fd937751..56e08348ff15e 100644
--- a/tests/cases/fourslash/defaultParamsAndContextualTypes.ts
+++ b/tests/cases/fourslash/defaultParamsAndContextualTypes.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts"/>
 
+// @strict: false
 ////interface FooOptions {
 ////    text?: string;
 ////}
diff --git a/tests/cases/fourslash/deprecatedInheritedJSDocOverload.ts b/tests/cases/fourslash/deprecatedInheritedJSDocOverload.ts
index 838d984bae0a9..1cb1cc35d4a6e 100644
--- a/tests/cases/fourslash/deprecatedInheritedJSDocOverload.ts
+++ b/tests/cases/fourslash/deprecatedInheritedJSDocOverload.ts
@@ -1,3 +1,4 @@
+// @strict: false
 
 //// interface PartialObserver<T> {}
 //// interface Subscription {}
diff --git a/tests/cases/fourslash/derivedTypeIndexerWithGenericConstraints.ts b/tests/cases/fourslash/derivedTypeIndexerWithGenericConstraints.ts
index 82dfe9429e1b2..a11a5976b6f75 100644
--- a/tests/cases/fourslash/derivedTypeIndexerWithGenericConstraints.ts
+++ b/tests/cases/fourslash/derivedTypeIndexerWithGenericConstraints.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////class CollectionItem {
 ////    x: number;
 ////}
diff --git a/tests/cases/fourslash/diagnosticsJsFileCompilationDuplicateFunctionImplementation.ts b/tests/cases/fourslash/diagnosticsJsFileCompilationDuplicateFunctionImplementation.ts
index 268944e010a39..01767fef7bc5f 100644
--- a/tests/cases/fourslash/diagnosticsJsFileCompilationDuplicateFunctionImplementation.ts
+++ b/tests/cases/fourslash/diagnosticsJsFileCompilationDuplicateFunctionImplementation.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 // @declaration: true
 // @newLine: lf
 // @outFile: out.js
diff --git a/tests/cases/fourslash/emptyArrayInference.ts b/tests/cases/fourslash/emptyArrayInference.ts
index 195acdf33d5c2..a7ed3da94ac95 100644
--- a/tests/cases/fourslash/emptyArrayInference.ts
+++ b/tests/cases/fourslash/emptyArrayInference.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////var x/*1*/x = true ? [1] : [undefined]; 
 ////var y/*2*/y = true ? [1] : [];
 
diff --git a/tests/cases/fourslash/exportEqualTypes.ts b/tests/cases/fourslash/exportEqualTypes.ts
index 0853fc9fc791f..f5f14433c14ee 100644
--- a/tests/cases/fourslash/exportEqualTypes.ts
+++ b/tests/cases/fourslash/exportEqualTypes.ts
@@ -1,5 +1,6 @@
 /// <reference path='./fourslash.ts'/>
 
+// @strict: false
 // @Filename: exportEqualTypes_file0.ts
 ////interface x {
 ////    (): Date;
diff --git a/tests/cases/fourslash/extendArrayInterfaceMember.ts b/tests/cases/fourslash/extendArrayInterfaceMember.ts
index cc1460b126e54..ee1eb812769ab 100644
--- a/tests/cases/fourslash/extendArrayInterfaceMember.ts
+++ b/tests/cases/fourslash/extendArrayInterfaceMember.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts"/>
 
+// @strict: false
 ////var x = [1, 2, 3];
 ////var /*y*/y = x.pop(/*1*/5/*2*/);
 ////
diff --git a/tests/cases/fourslash/extendInterfaceOverloadedMethod.ts b/tests/cases/fourslash/extendInterfaceOverloadedMethod.ts
index dd4332c24736b..4d172cdf4ff98 100644
--- a/tests/cases/fourslash/extendInterfaceOverloadedMethod.ts
+++ b/tests/cases/fourslash/extendInterfaceOverloadedMethod.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////interface A<T> {
 ////    foo(a: T): B<T>;
 ////    foo(): void ;
diff --git a/tests/cases/fourslash/extendsTArray.ts b/tests/cases/fourslash/extendsTArray.ts
index 8f655b9db4591..c305c7ca85090 100644
--- a/tests/cases/fourslash/extendsTArray.ts
+++ b/tests/cases/fourslash/extendsTArray.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////interface I1<T> {
 ////    (a: T): T;
 ////}
diff --git a/tests/cases/fourslash/extractFunctionContainingThis3.ts b/tests/cases/fourslash/extractFunctionContainingThis3.ts
index 505f241239ac2..cef16f5fb180f 100644
--- a/tests/cases/fourslash/extractFunctionContainingThis3.ts
+++ b/tests/cases/fourslash/extractFunctionContainingThis3.ts
@@ -1,6 +1,7 @@
 /// <reference path='fourslash.ts' />
 
 
+// @strict: false
 ////const foo = {
 ////    bar: "1",
 ////    baz() {
diff --git a/tests/cases/fourslash/fixingTypeParametersQuickInfo.ts b/tests/cases/fourslash/fixingTypeParametersQuickInfo.ts
index fb7fcb69cc572..b9974c1aaa182 100644
--- a/tests/cases/fourslash/fixingTypeParametersQuickInfo.ts
+++ b/tests/cases/fourslash/fixingTypeParametersQuickInfo.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////declare function f<T>(x: T, y: (p: T) => T, z: (p: T) => T): T;
 ////var /*1*/result = /*2*/f(0, /*3*/x => null, /*4*/x => x.blahblah);
 
diff --git a/tests/cases/fourslash/functionTypes.ts b/tests/cases/fourslash/functionTypes.ts
index 222bbf2fd97fb..2b2e7876891aa 100644
--- a/tests/cases/fourslash/functionTypes.ts
+++ b/tests/cases/fourslash/functionTypes.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////var f: Function;
 ////function g() { }
 ////
diff --git a/tests/cases/fourslash/genericInterfacePropertyInference1.ts b/tests/cases/fourslash/genericInterfacePropertyInference1.ts
index 60f4cf0dda3d1..6e2595e73cf2c 100644
--- a/tests/cases/fourslash/genericInterfacePropertyInference1.ts
+++ b/tests/cases/fourslash/genericInterfacePropertyInference1.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////interface I {
 ////    x: number;
 ////}
diff --git a/tests/cases/fourslash/genericInterfacePropertyInference2.ts b/tests/cases/fourslash/genericInterfacePropertyInference2.ts
index a3600865a9e5b..0f6ea7d0e93a9 100644
--- a/tests/cases/fourslash/genericInterfacePropertyInference2.ts
+++ b/tests/cases/fourslash/genericInterfacePropertyInference2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////interface I {
 ////    x: number;
 ////}
diff --git a/tests/cases/fourslash/genericMapTyping1.ts b/tests/cases/fourslash/genericMapTyping1.ts
index 47514c9616829..3623d417b93fe 100644
--- a/tests/cases/fourslash/genericMapTyping1.ts
+++ b/tests/cases/fourslash/genericMapTyping1.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 ////interface Iterator_<T, U> {
 ////    (value: T, index: any, list: any): U;
 ////}
diff --git a/tests/cases/fourslash/genericObjectBaseType.ts b/tests/cases/fourslash/genericObjectBaseType.ts
index acca6c3c33b8f..e4acbdbcd344e 100644
--- a/tests/cases/fourslash/genericObjectBaseType.ts
+++ b/tests/cases/fourslash/genericObjectBaseType.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// class C<T> {
 ////     constructor(){}
 ////     foo(a: T) {
diff --git a/tests/cases/fourslash/genericRespecialization1.ts b/tests/cases/fourslash/genericRespecialization1.ts
index 3264052aea9c5..e69742b6653cf 100644
--- a/tests/cases/fourslash/genericRespecialization1.ts
+++ b/tests/cases/fourslash/genericRespecialization1.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// class Food {
 ////     private amount: number;
 ////     constructor(public name: string) {
diff --git a/tests/cases/fourslash/getDeclarationDiagnostics.ts b/tests/cases/fourslash/getDeclarationDiagnostics.ts
index 575586efb9459..3a35f8240423e 100644
--- a/tests/cases/fourslash/getDeclarationDiagnostics.ts
+++ b/tests/cases/fourslash/getDeclarationDiagnostics.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 // @declaration: true
 // @outFile: true
 
diff --git a/tests/cases/fourslash/getSemanticDiagnosticForDeclaration.ts b/tests/cases/fourslash/getSemanticDiagnosticForDeclaration.ts
index 72739c665be62..b27f86c768830 100644
--- a/tests/cases/fourslash/getSemanticDiagnosticForDeclaration.ts
+++ b/tests/cases/fourslash/getSemanticDiagnosticForDeclaration.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 // @module: CommonJS
 // @declaration: true
 //// export function /*1*/foo/*2*/() {
diff --git a/tests/cases/fourslash/incompatibleOverride.ts b/tests/cases/fourslash/incompatibleOverride.ts
index 1ce0b07def189..155a88c5972e5 100644
--- a/tests/cases/fourslash/incompatibleOverride.ts
+++ b/tests/cases/fourslash/incompatibleOverride.ts
@@ -2,6 +2,7 @@
 
 // Squiggle for implementing a derived class with an incompatible override is too large
 
+// @strict: false
 //// class Foo { xyz: string; }
 //// class Bar extends Foo { /*1*/xyz/*2*/: number = 1; }
 //// class Baz extends Foo { public /*3*/xyz/*4*/: number = 2; }
diff --git a/tests/cases/fourslash/inheritedModuleMembersForClodule2.ts b/tests/cases/fourslash/inheritedModuleMembersForClodule2.ts
index 8c1150be0c748..87139fce98541 100644
--- a/tests/cases/fourslash/inheritedModuleMembersForClodule2.ts
+++ b/tests/cases/fourslash/inheritedModuleMembersForClodule2.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 ////namespace M {
 ////    export namespace A {
 ////        var o;
diff --git a/tests/cases/fourslash/invertedCloduleAfterQuickInfo.ts b/tests/cases/fourslash/invertedCloduleAfterQuickInfo.ts
index 7c593913bb0f5..ce6ec86e26d13 100644
--- a/tests/cases/fourslash/invertedCloduleAfterQuickInfo.ts
+++ b/tests/cases/fourslash/invertedCloduleAfterQuickInfo.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 ////namespace M {
 ////    namespace A {
 ////        var o;
diff --git a/tests/cases/fourslash/jsxAttributeSnippetCompletionAfterTypeArgs.ts b/tests/cases/fourslash/jsxAttributeSnippetCompletionAfterTypeArgs.ts
index f22d6a7c86e4f..6b0ef2e2f62b6 100644
--- a/tests/cases/fourslash/jsxAttributeSnippetCompletionAfterTypeArgs.ts
+++ b/tests/cases/fourslash/jsxAttributeSnippetCompletionAfterTypeArgs.ts
@@ -1,4 +1,5 @@
 /// <reference path="fourslash.ts" />
+// @strict: false
 //@Filename: file.tsx
 
 ////declare const React: any;
diff --git a/tests/cases/fourslash/jsxAttributeSnippetCompletionClosed.ts b/tests/cases/fourslash/jsxAttributeSnippetCompletionClosed.ts
index 636c5bb1ab23c..b73a15acae97e 100644
--- a/tests/cases/fourslash/jsxAttributeSnippetCompletionClosed.ts
+++ b/tests/cases/fourslash/jsxAttributeSnippetCompletionClosed.ts
@@ -1,4 +1,5 @@
 /// <reference path="fourslash.ts" />
+// @strict: false
 //@Filename: file.tsx
 ////interface NestedInterface {
 ////    Foo: NestedInterface;
diff --git a/tests/cases/fourslash/jsxAttributeSnippetCompletionUnclosed.ts b/tests/cases/fourslash/jsxAttributeSnippetCompletionUnclosed.ts
index 5816f56500d10..1581047f114fa 100644
--- a/tests/cases/fourslash/jsxAttributeSnippetCompletionUnclosed.ts
+++ b/tests/cases/fourslash/jsxAttributeSnippetCompletionUnclosed.ts
@@ -1,4 +1,5 @@
 /// <reference path="fourslash.ts" />
+// @strict: false
 //@Filename: file.tsx
 ////interface NestedInterface {
 ////    Foo: NestedInterface;
diff --git a/tests/cases/fourslash/multiModuleFundule.ts b/tests/cases/fourslash/multiModuleFundule.ts
index 8856759144b16..b7d23b482ccd8 100644
--- a/tests/cases/fourslash/multiModuleFundule.ts
+++ b/tests/cases/fourslash/multiModuleFundule.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////function C(x: number) { }
 ////
 ////namespace C {
diff --git a/tests/cases/fourslash/noSuggestionDiagnosticsOnParseError.ts b/tests/cases/fourslash/noSuggestionDiagnosticsOnParseError.ts
index c36d5352e7fd7..0f6569bacdc2b 100644
--- a/tests/cases/fourslash/noSuggestionDiagnosticsOnParseError.ts
+++ b/tests/cases/fourslash/noSuggestionDiagnosticsOnParseError.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @Filename: /a.ts
 ////export {};
 ////const a = 1 d;
diff --git a/tests/cases/fourslash/objectLiteralCallSignatures.ts b/tests/cases/fourslash/objectLiteralCallSignatures.ts
index 3749d26fb4e62..7926af77395f7 100644
--- a/tests/cases/fourslash/objectLiteralCallSignatures.ts
+++ b/tests/cases/fourslash/objectLiteralCallSignatures.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////var /*1*/x: {
 ////    func1(x: number): number;         // Method signature
 ////    func2: (x: number) => number;     // Function type literal
diff --git a/tests/cases/fourslash/parenthesisFatArrows.ts b/tests/cases/fourslash/parenthesisFatArrows.ts
index ea123b986e447..2bdc235e76b03 100644
--- a/tests/cases/fourslash/parenthesisFatArrows.ts
+++ b/tests/cases/fourslash/parenthesisFatArrows.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts"/>
 
+// @strict: false
 ////x => x;
 ////(y) => y;
 /////**/
diff --git a/tests/cases/fourslash/pasteLambdaOverModule.ts b/tests/cases/fourslash/pasteLambdaOverModule.ts
index f85b9d902c21a..5637baac373dc 100644
--- a/tests/cases/fourslash/pasteLambdaOverModule.ts
+++ b/tests/cases/fourslash/pasteLambdaOverModule.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 //// /**/
 
 goTo.marker();
diff --git a/tests/cases/fourslash/quickInfoForContextuallyTypedFunctionInTaggedTemplateExpression2.ts b/tests/cases/fourslash/quickInfoForContextuallyTypedFunctionInTaggedTemplateExpression2.ts
index 0c72575d936ac..12fbd6865dfe4 100644
--- a/tests/cases/fourslash/quickInfoForContextuallyTypedFunctionInTaggedTemplateExpression2.ts
+++ b/tests/cases/fourslash/quickInfoForContextuallyTypedFunctionInTaggedTemplateExpression2.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 ////function tempTag2(templateStrs: TemplateStringsArray, f: (x: number) => number, x: number): number;
 ////function tempTag2(templateStrs: TemplateStringsArray, f: (x: string) => string, h: (y: string) => string, x: string): string;
 ////function tempTag2(...rest: any[]): any {
diff --git a/tests/cases/fourslash/quickInfoForObjectBindingElementPropertyName03.ts b/tests/cases/fourslash/quickInfoForObjectBindingElementPropertyName03.ts
index 9378c99126c64..aadd48680f7d1 100644
--- a/tests/cases/fourslash/quickInfoForObjectBindingElementPropertyName03.ts
+++ b/tests/cases/fourslash/quickInfoForObjectBindingElementPropertyName03.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////interface Recursive {
 ////    next?: Recursive;
 ////    value: any;
diff --git a/tests/cases/fourslash/quickInfoForShorthandProperty.ts b/tests/cases/fourslash/quickInfoForShorthandProperty.ts
index c863663eff060..6dd36a29b3c39 100644
--- a/tests/cases/fourslash/quickInfoForShorthandProperty.ts
+++ b/tests/cases/fourslash/quickInfoForShorthandProperty.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// var name1 = undefined, id1 = undefined;
 //// var /*obj1*/obj1 = {/*name1*/name1, /*id1*/id1};
 //// var name2 = "Hello";
diff --git a/tests/cases/fourslash/quickInfoGenericTypeArgumentInference1.ts b/tests/cases/fourslash/quickInfoGenericTypeArgumentInference1.ts
index 3b8bff11dca22..837e48ea82692 100644
--- a/tests/cases/fourslash/quickInfoGenericTypeArgumentInference1.ts
+++ b/tests/cases/fourslash/quickInfoGenericTypeArgumentInference1.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////namespace Underscore {
 ////    export interface Iterator<T, U> {
 ////        (value: T, index: any, list: any): U;
diff --git a/tests/cases/fourslash/quickInfoJsDocNonDiscriminatedUnionSharedProp.ts b/tests/cases/fourslash/quickInfoJsDocNonDiscriminatedUnionSharedProp.ts
index ad4300f2696dd..18fb506d05cae 100644
--- a/tests/cases/fourslash/quickInfoJsDocNonDiscriminatedUnionSharedProp.ts
+++ b/tests/cases/fourslash/quickInfoJsDocNonDiscriminatedUnionSharedProp.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 //// interface Entries {
 ////   /**
 ////    * Plugins info...
diff --git a/tests/cases/fourslash/quickInfoOnCatchVariable.ts b/tests/cases/fourslash/quickInfoOnCatchVariable.ts
index 07e86c2ed818f..f6c4ba3e6729c 100644
--- a/tests/cases/fourslash/quickInfoOnCatchVariable.ts
+++ b/tests/cases/fourslash/quickInfoOnCatchVariable.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 //// function f() {
 ////    try { } catch (/**/e) { }
 //// }
diff --git a/tests/cases/fourslash/quickInfoOnMergedInterfacesWithIncrementalEdits.ts b/tests/cases/fourslash/quickInfoOnMergedInterfacesWithIncrementalEdits.ts
index d3bbb125e8d20..46540ac07f6b1 100644
--- a/tests/cases/fourslash/quickInfoOnMergedInterfacesWithIncrementalEdits.ts
+++ b/tests/cases/fourslash/quickInfoOnMergedInterfacesWithIncrementalEdits.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////namespace MM {
 ////    interface B<T> {
 ////        foo: number;
diff --git a/tests/cases/fourslash/quickInfoOnMergedModule.ts b/tests/cases/fourslash/quickInfoOnMergedModule.ts
index b9225e2b0bc09..8d8d7a3781b78 100644
--- a/tests/cases/fourslash/quickInfoOnMergedModule.ts
+++ b/tests/cases/fourslash/quickInfoOnMergedModule.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////namespace M2 {
 ////    export interface A {
 ////        foo: string;
diff --git a/tests/cases/fourslash/quickInfoOnNarrowedTypeInModule.ts b/tests/cases/fourslash/quickInfoOnNarrowedTypeInModule.ts
index 2f834c9515b8d..b5d9ee7f933f9 100644
--- a/tests/cases/fourslash/quickInfoOnNarrowedTypeInModule.ts
+++ b/tests/cases/fourslash/quickInfoOnNarrowedTypeInModule.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////var strOrNum: string | number;
 ////namespace m {
 ////    var nonExportedStrOrNum: string | number;
diff --git a/tests/cases/fourslash/quickInfoSignatureOptionalParameterFromUnion1.ts b/tests/cases/fourslash/quickInfoSignatureOptionalParameterFromUnion1.ts
index dce4bfdf0ad56..56b17d9c59cde 100644
--- a/tests/cases/fourslash/quickInfoSignatureOptionalParameterFromUnion1.ts
+++ b/tests/cases/fourslash/quickInfoSignatureOptionalParameterFromUnion1.ts
@@ -2,6 +2,7 @@
 
 // https://github.com/microsoft/TypeScript/issues/55574
 
+// @strict: false
 //// declare const optionals:
 ////   | ((a?: { a: true }) => unknown)
 ////   | ((b?: { b: true }) => unknown);
diff --git a/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion2.ts b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion2.ts
index d53beebd5d8cc..0707d8f69f8ee 100644
--- a/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion2.ts
+++ b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion2.ts
@@ -2,6 +2,7 @@
 
 // https://github.com/microsoft/TypeScript/issues/55574
 
+// @strict: false
 //// declare const rest:
 ////   | ((a?: { a: true }, ...rest: string[]) => unknown)
 ////   | ((b?: { b: true }) => unknown);
diff --git a/tests/cases/fourslash/quickInfoWidenedTypes.ts b/tests/cases/fourslash/quickInfoWidenedTypes.ts
index 1ece274690bd7..3d69b22dea4b3 100644
--- a/tests/cases/fourslash/quickInfoWidenedTypes.ts
+++ b/tests/cases/fourslash/quickInfoWidenedTypes.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////var /*1*/a = null;                   // var a: any
 ////var /*2*/b = undefined;              // var b: any
 ////var /*3*/c = { x: 0, y: null };	// var c: { x: number, y: any }
diff --git a/tests/cases/fourslash/refactorConvertToGetAccessAndSetAccess10.ts b/tests/cases/fourslash/refactorConvertToGetAccessAndSetAccess10.ts
index 7161dd18d7cfa..fdf5e3d28192c 100644
--- a/tests/cases/fourslash/refactorConvertToGetAccessAndSetAccess10.ts
+++ b/tests/cases/fourslash/refactorConvertToGetAccessAndSetAccess10.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 //// class A {
 ////     /*a*/public a?: string = "foo";/*b*/
 //// }
diff --git a/tests/cases/fourslash/signatureHelpCallExpressionJs.ts b/tests/cases/fourslash/signatureHelpCallExpressionJs.ts
index 3b19ddb393ac5..db7e19c383cd1 100644
--- a/tests/cases/fourslash/signatureHelpCallExpressionJs.ts
+++ b/tests/cases/fourslash/signatureHelpCallExpressionJs.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 // @checkJs: true
 // @allowJs: true
 
diff --git a/tests/cases/fourslash/signatureHelpOptionalCall2.ts b/tests/cases/fourslash/signatureHelpOptionalCall2.ts
index ab388398177a0..0a400444c2440 100644
--- a/tests/cases/fourslash/signatureHelpOptionalCall2.ts
+++ b/tests/cases/fourslash/signatureHelpOptionalCall2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////declare const fnTest: undefined | ((str: string, num: number) => void);
 ////fnTest?.(/*1*/);
 
diff --git a/tests/cases/fourslash/squiggleFunctionExpression.ts b/tests/cases/fourslash/squiggleFunctionExpression.ts
index 75cca339e9daf..1d28f445d7cc2 100644
--- a/tests/cases/fourslash/squiggleFunctionExpression.ts
+++ b/tests/cases/fourslash/squiggleFunctionExpression.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts"/>
 
+// @strict: false
 ////function takesCallback(callback: (n) => any) { }
 ////takesCallback(function inner(n) { var /*1*/k/*2*/: string = 10; });
 
diff --git a/tests/cases/fourslash/squiggleIllegalSubclassOverride.ts b/tests/cases/fourslash/squiggleIllegalSubclassOverride.ts
index c97c6c75fcf5b..103fd13132cc6 100644
--- a/tests/cases/fourslash/squiggleIllegalSubclassOverride.ts
+++ b/tests/cases/fourslash/squiggleIllegalSubclassOverride.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts"/>
 
+// @strict: false
 ////class Foo {
 ////    public x: number;
 ////}
diff --git a/tests/cases/fourslash/superInDerivedTypeOfGenericWithStatics.ts b/tests/cases/fourslash/superInDerivedTypeOfGenericWithStatics.ts
index 03ff229fd582f..5472c1d1eebd4 100644
--- a/tests/cases/fourslash/superInDerivedTypeOfGenericWithStatics.ts
+++ b/tests/cases/fourslash/superInDerivedTypeOfGenericWithStatics.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts'/>
 
+// @strict: false
 ////namespace M {
 ////   export class C<T extends Date> {
 ////      static foo(): C<Date> {
diff --git a/tests/cases/fourslash/unclosedArrayErrorRecovery.ts b/tests/cases/fourslash/unclosedArrayErrorRecovery.ts
index 3d9e4acea5351..790fc72cf60f1 100644
--- a/tests/cases/fourslash/unclosedArrayErrorRecovery.ts
+++ b/tests/cases/fourslash/unclosedArrayErrorRecovery.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 ////var table: number[;
 /////**/table.push(1)
 
diff --git a/tests/cases/fourslash/underscoreTypings02.ts b/tests/cases/fourslash/underscoreTypings02.ts
index be7d20427e229..bf7fdeaca1d69 100644
--- a/tests/cases/fourslash/underscoreTypings02.ts
+++ b/tests/cases/fourslash/underscoreTypings02.ts
@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 
+// @strict: false
 // @module: CommonJS
 
 //// interface Dictionary<T> {
diff --git a/tests/cases/fourslash/unusedClassInNamespace4.ts b/tests/cases/fourslash/unusedClassInNamespace4.ts
index 8b856379acbf0..ecbc7f213a8c9 100644
--- a/tests/cases/fourslash/unusedClassInNamespace4.ts
+++ b/tests/cases/fourslash/unusedClassInNamespace4.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noUnusedLocals: true
 // @noUnusedParameters:true
 //// [| namespace Validation {
diff --git a/tests/cases/fourslash/unusedParameterInFunction2.ts b/tests/cases/fourslash/unusedParameterInFunction2.ts
index 96a710df911f0..c53aedad6d56c 100644
--- a/tests/cases/fourslash/unusedParameterInFunction2.ts
+++ b/tests/cases/fourslash/unusedParameterInFunction2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noUnusedParameters: true
 ////function [|greeter(x,y)|] {
 ////    use(x);
diff --git a/tests/cases/fourslash/unusedParameterInLambda3.ts b/tests/cases/fourslash/unusedParameterInLambda3.ts
index 20742f4bd3778..a478baf950ca8 100644
--- a/tests/cases/fourslash/unusedParameterInLambda3.ts
+++ b/tests/cases/fourslash/unusedParameterInLambda3.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noUnusedLocals: true
 // @noUnusedParameters: true
 ////[|/*~a*/(/*~b*/x/*~c*/,/*~d*/y/*~e*/)/*~f*/ => /*~g*/x/*~h*/|]
diff --git a/tests/cases/fourslash/unusedTypeParametersInLambda3.ts b/tests/cases/fourslash/unusedTypeParametersInLambda3.ts
index 764e75294b9bb..937865a5916d6 100644
--- a/tests/cases/fourslash/unusedTypeParametersInLambda3.ts
+++ b/tests/cases/fourslash/unusedTypeParametersInLambda3.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noUnusedLocals: true
 // @noUnusedParameters: true
 //// class A<Dummy> { public x: Dummy }
diff --git a/tests/cases/fourslash/unusedTypeParametersInLambda4.ts b/tests/cases/fourslash/unusedTypeParametersInLambda4.ts
index 14bdb64549b51..a1cd928745c3b 100644
--- a/tests/cases/fourslash/unusedTypeParametersInLambda4.ts
+++ b/tests/cases/fourslash/unusedTypeParametersInLambda4.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noUnusedParameters: true
 //// class A<T> {
 ////    public x: T;
diff --git a/tests/cases/fourslash/unusedVariableInClass1.ts b/tests/cases/fourslash/unusedVariableInClass1.ts
index 9e7235841c938..66d18087325cf 100644
--- a/tests/cases/fourslash/unusedVariableInClass1.ts
+++ b/tests/cases/fourslash/unusedVariableInClass1.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noUnusedLocals: true
 ////class greeter {
 ////    [|private greeting: string;|]
diff --git a/tests/cases/fourslash/unusedVariableInClass2.ts b/tests/cases/fourslash/unusedVariableInClass2.ts
index a4302b4dd535a..d183580601e7a 100644
--- a/tests/cases/fourslash/unusedVariableInClass2.ts
+++ b/tests/cases/fourslash/unusedVariableInClass2.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noUnusedLocals: true
 ////class greeter {
 ////    [|public greeting1;
diff --git a/tests/cases/fourslash/unusedVariableInClass4.ts b/tests/cases/fourslash/unusedVariableInClass4.ts
index ec5d5f973a2d6..f3ab0bad887ea 100644
--- a/tests/cases/fourslash/unusedVariableInClass4.ts
+++ b/tests/cases/fourslash/unusedVariableInClass4.ts
@@ -1,5 +1,6 @@
 /// <reference path='fourslash.ts' />
 
+// @strict: false
 // @noUnusedLocals: false
 ////class greeter {
 ////    [|private greeting: string;|]