diff --git a/tests/baselines/reference/checkJsFiles.errors.txt b/tests/baselines/reference/checkJsFiles.errors.txt
new file mode 100644
index 00000000000..8371e101dd1
--- /dev/null
+++ b/tests/baselines/reference/checkJsFiles.errors.txt
@@ -0,0 +1,13 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
+  Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
+tests/cases/compiler/a.js(3,1): error TS2322: Type '0' is not assignable to type 'string'.
+
+
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
+!!! error TS5055:   Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
+==== tests/cases/compiler/a.js (1 errors) ====
+    
+    var x = "string";
+    x = 0;
+    ~
+!!! error TS2322: Type '0' is not assignable to type 'string'.
\ No newline at end of file
diff --git a/tests/baselines/reference/checkJsFiles2.errors.txt b/tests/baselines/reference/checkJsFiles2.errors.txt
new file mode 100644
index 00000000000..566ba3786b8
--- /dev/null
+++ b/tests/baselines/reference/checkJsFiles2.errors.txt
@@ -0,0 +1,14 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
+  Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
+tests/cases/compiler/a.js(4,1): error TS2322: Type '0' is not assignable to type 'string'.
+
+
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
+!!! error TS5055:   Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
+==== tests/cases/compiler/a.js (1 errors) ====
+    
+    // @check
+    var x = "string";
+    x = 0;
+    ~
+!!! error TS2322: Type '0' is not assignable to type 'string'.
\ No newline at end of file
diff --git a/tests/baselines/reference/checkJsFiles3.errors.txt b/tests/baselines/reference/checkJsFiles3.errors.txt
new file mode 100644
index 00000000000..566ba3786b8
--- /dev/null
+++ b/tests/baselines/reference/checkJsFiles3.errors.txt
@@ -0,0 +1,14 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
+  Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
+tests/cases/compiler/a.js(4,1): error TS2322: Type '0' is not assignable to type 'string'.
+
+
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
+!!! error TS5055:   Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
+==== tests/cases/compiler/a.js (1 errors) ====
+    
+    // @check
+    var x = "string";
+    x = 0;
+    ~
+!!! error TS2322: Type '0' is not assignable to type 'string'.
\ No newline at end of file
diff --git a/tests/cases/compiler/checkJsFiles.ts b/tests/cases/compiler/checkJsFiles.ts
new file mode 100644
index 00000000000..c36673b0239
--- /dev/null
+++ b/tests/cases/compiler/checkJsFiles.ts
@@ -0,0 +1,6 @@
+// @allowJs: true
+// @checkJsFiles: true
+
+// @fileName: a.js
+var x = "string";
+x = 0;
\ No newline at end of file
diff --git a/tests/cases/compiler/checkJsFiles2.ts b/tests/cases/compiler/checkJsFiles2.ts
new file mode 100644
index 00000000000..fe8978666b0
--- /dev/null
+++ b/tests/cases/compiler/checkJsFiles2.ts
@@ -0,0 +1,7 @@
+// @allowJs: true
+// @checkJsFiles: false
+
+// @fileName: a.js
+// @check
+var x = "string";
+x = 0;
\ No newline at end of file
diff --git a/tests/cases/compiler/checkJsFiles3.ts b/tests/cases/compiler/checkJsFiles3.ts
new file mode 100644
index 00000000000..964f909bc6f
--- /dev/null
+++ b/tests/cases/compiler/checkJsFiles3.ts
@@ -0,0 +1,6 @@
+// @allowJs: true
+
+// @fileName: a.js
+// @check
+var x = "string";
+x = 0;
\ No newline at end of file