diff --git a/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementation.errors.txt b/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementation.errors.txt
new file mode 100644
index 00000000000..fb0c214ddf6
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementation.errors.txt
@@ -0,0 +1,15 @@
+tests/cases/compiler/a.ts(1,10): error TS2393: Duplicate function implementation.
+
+
+==== tests/cases/compiler/b.js (0 errors) ====
+    function foo() {
+        return 10;
+    }
+==== tests/cases/compiler/a.ts (1 errors) ====
+    function foo() {
+             ~~~
+!!! error TS2393: Duplicate function implementation.
+        return 30;
+    }
+    
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementation.js b/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementation.js
new file mode 100644
index 00000000000..9b644509361
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementation.js
@@ -0,0 +1,23 @@
+//// [tests/cases/compiler/jsFileCompilationDuplicateFunctionImplementation.ts] ////
+
+//// [b.js]
+function foo() {
+    return 10;
+}
+//// [a.ts]
+function foo() {
+    return 30;
+}
+
+
+
+//// [out.js]
+function foo() {
+    return 10;
+}
+function foo() {
+    return 30;
+}
+
+
+//// [out.d.ts]
diff --git a/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.errors.txt b/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.errors.txt
new file mode 100644
index 00000000000..78eb22546e8
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.errors.txt
@@ -0,0 +1,16 @@
+tests/cases/compiler/a.ts(1,10): error TS2393: Duplicate function implementation.
+
+
+==== tests/cases/compiler/a.ts (1 errors) ====
+    function foo() {
+             ~~~
+!!! error TS2393: Duplicate function implementation.
+        return 30;
+    }
+    
+==== tests/cases/compiler/b.js (0 errors) ====
+    function foo() {
+        return 10;
+    }
+    
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.js b/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.js
new file mode 100644
index 00000000000..d7965e91be1
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.js
@@ -0,0 +1,24 @@
+//// [tests/cases/compiler/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.ts] ////
+
+//// [a.ts]
+function foo() {
+    return 30;
+}
+
+//// [b.js]
+function foo() {
+    return 10;
+}
+
+
+
+//// [out.js]
+function foo() {
+    return 30;
+}
+function foo() {
+    return 10;
+}
+
+
+//// [out.d.ts]
diff --git a/tests/cases/compiler/jsFileCompilationDuplicateFunctionImplementation.ts b/tests/cases/compiler/jsFileCompilationDuplicateFunctionImplementation.ts
new file mode 100644
index 00000000000..1cc61edaf32
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilationDuplicateFunctionImplementation.ts
@@ -0,0 +1,12 @@
+// @jsExtensions: js
+// @out: out.js
+// @declaration: true
+// @filename: b.js
+function foo() {
+    return 10;
+}
+// @filename: a.ts
+function foo() {
+    return 30;
+}
+
diff --git a/tests/cases/compiler/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.ts b/tests/cases/compiler/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.ts
new file mode 100644
index 00000000000..af1d842d9b2
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.ts
@@ -0,0 +1,13 @@
+// @jsExtensions: js
+// @out: out.js
+// @declaration: true
+// @filename: a.ts
+function foo() {
+    return 30;
+}
+
+// @filename: b.js
+function foo() {
+    return 10;
+}
+