diff --git a/tests/baselines/reference/classAndInterfaceMergeConflictingMembers.errors.txt b/tests/baselines/reference/classAndInterfaceMergeConflictingMembers.errors.txt
new file mode 100644
index 00000000000..48e52faae1e
--- /dev/null
+++ b/tests/baselines/reference/classAndInterfaceMergeConflictingMembers.errors.txt
@@ -0,0 +1,44 @@
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(2,12): error TS2300: Duplicate identifier 'x'.
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(6,5): error TS2300: Duplicate identifier 'x'.
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(10,15): error TS2300: Duplicate identifier 'x'.
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(14,5): error TS2300: Duplicate identifier 'x'.
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(18,13): error TS2300: Duplicate identifier 'x'.
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(22,5): error TS2300: Duplicate identifier 'x'.
+
+
+==== tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts (6 errors) ====
+    declare class C1 {
+        public x : number;
+               ~
+!!! error TS2300: Duplicate identifier 'x'.
+    }
+    
+    interface C1 {
+        x : number;
+        ~
+!!! error TS2300: Duplicate identifier 'x'.
+    }
+    
+    declare class C2 {
+        protected x : number;
+                  ~
+!!! error TS2300: Duplicate identifier 'x'.
+    }
+    
+    interface C2 {
+        x : number;
+        ~
+!!! error TS2300: Duplicate identifier 'x'.
+    }
+    
+    declare class C3 {
+        private x : number;
+                ~
+!!! error TS2300: Duplicate identifier 'x'.
+    }
+    
+    interface C3 {
+        x : number;
+        ~
+!!! error TS2300: Duplicate identifier 'x'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/classAndInterfaceMergeConflictingMembers.js b/tests/baselines/reference/classAndInterfaceMergeConflictingMembers.js
new file mode 100644
index 00000000000..07b425383f4
--- /dev/null
+++ b/tests/baselines/reference/classAndInterfaceMergeConflictingMembers.js
@@ -0,0 +1,26 @@
+//// [classAndInterfaceMergeConflictingMembers.ts]
+declare class C1 {
+    public x : number;
+}
+
+interface C1 {
+    x : number;
+}
+
+declare class C2 {
+    protected x : number;
+}
+
+interface C2 {
+    x : number;
+}
+
+declare class C3 {
+    private x : number;
+}
+
+interface C3 {
+    x : number;
+}
+
+//// [classAndInterfaceMergeConflictingMembers.js]
diff --git a/tests/baselines/reference/declaredClassMergedwithSelf.errors.txt b/tests/baselines/reference/declaredClassMergedwithSelf.errors.txt
new file mode 100644
index 00000000000..8a783639c1c
--- /dev/null
+++ b/tests/baselines/reference/declaredClassMergedwithSelf.errors.txt
@@ -0,0 +1,27 @@
+tests/cases/conformance/classes/classDeclarations/declaredClassMergedwithSelf.ts(1,15): error TS2300: Duplicate identifier 'C1'.
+tests/cases/conformance/classes/classDeclarations/declaredClassMergedwithSelf.ts(3,15): error TS2300: Duplicate identifier 'C1'.
+tests/cases/conformance/classes/classDeclarations/declaredClassMergedwithSelf.ts(5,15): error TS2300: Duplicate identifier 'C2'.
+tests/cases/conformance/classes/classDeclarations/declaredClassMergedwithSelf.ts(7,11): error TS2300: Duplicate identifier 'C2'.
+tests/cases/conformance/classes/classDeclarations/declaredClassMergedwithSelf.ts(9,15): error TS2300: Duplicate identifier 'C2'.
+
+
+==== tests/cases/conformance/classes/classDeclarations/declaredClassMergedwithSelf.ts (5 errors) ====
+    declare class C1 {}
+                  ~~
+!!! error TS2300: Duplicate identifier 'C1'.
+    
+    declare class C1 {}
+                  ~~
+!!! error TS2300: Duplicate identifier 'C1'.
+    
+    declare class C2 {}
+                  ~~
+!!! error TS2300: Duplicate identifier 'C2'.
+    
+    interface C2 {}
+              ~~
+!!! error TS2300: Duplicate identifier 'C2'.
+    
+    declare class C2 {}
+                  ~~
+!!! error TS2300: Duplicate identifier 'C2'.
\ No newline at end of file
diff --git a/tests/baselines/reference/declaredClassMergedwithSelf.js b/tests/baselines/reference/declaredClassMergedwithSelf.js
new file mode 100644
index 00000000000..85213668adc
--- /dev/null
+++ b/tests/baselines/reference/declaredClassMergedwithSelf.js
@@ -0,0 +1,12 @@
+//// [declaredClassMergedwithSelf.ts]
+declare class C1 {}
+
+declare class C1 {}
+
+declare class C2 {}
+
+interface C2 {}
+
+declare class C2 {}
+
+//// [declaredClassMergedwithSelf.js]
diff --git a/tests/baselines/reference/mergedClassInterface.js b/tests/baselines/reference/mergedClassInterface.js
new file mode 100644
index 00000000000..70c8b7d2b2f
--- /dev/null
+++ b/tests/baselines/reference/mergedClassInterface.js
@@ -0,0 +1,14 @@
+//// [mergedClassInterface.ts]
+declare class C1 {}
+
+interface C1 {}
+
+interface C2 {}
+
+declare class C2 {}
+
+interface C2 {}
+
+interface C2 {}
+
+//// [mergedClassInterface.js]
diff --git a/tests/baselines/reference/mergedClassInterface.symbols b/tests/baselines/reference/mergedClassInterface.symbols
new file mode 100644
index 00000000000..dc7ba891551
--- /dev/null
+++ b/tests/baselines/reference/mergedClassInterface.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/conformance/classes/classDeclarations/mergedClassInterface.ts ===
+declare class C1 {}
+>C1 : Symbol(C1, Decl(mergedClassInterface.ts, 0, 0), Decl(mergedClassInterface.ts, 0, 19))
+
+interface C1 {}
+>C1 : Symbol(C1, Decl(mergedClassInterface.ts, 0, 0), Decl(mergedClassInterface.ts, 0, 19))
+
+interface C2 {}
+>C2 : Symbol(C2, Decl(mergedClassInterface.ts, 2, 15), Decl(mergedClassInterface.ts, 4, 15), Decl(mergedClassInterface.ts, 6, 19), Decl(mergedClassInterface.ts, 8, 15))
+
+declare class C2 {}
+>C2 : Symbol(C2, Decl(mergedClassInterface.ts, 2, 15), Decl(mergedClassInterface.ts, 4, 15), Decl(mergedClassInterface.ts, 6, 19), Decl(mergedClassInterface.ts, 8, 15))
+
+interface C2 {}
+>C2 : Symbol(C2, Decl(mergedClassInterface.ts, 2, 15), Decl(mergedClassInterface.ts, 4, 15), Decl(mergedClassInterface.ts, 6, 19), Decl(mergedClassInterface.ts, 8, 15))
+
+interface C2 {}
+>C2 : Symbol(C2, Decl(mergedClassInterface.ts, 2, 15), Decl(mergedClassInterface.ts, 4, 15), Decl(mergedClassInterface.ts, 6, 19), Decl(mergedClassInterface.ts, 8, 15))
+
diff --git a/tests/baselines/reference/mergedClassInterface.types b/tests/baselines/reference/mergedClassInterface.types
new file mode 100644
index 00000000000..a31f147b734
--- /dev/null
+++ b/tests/baselines/reference/mergedClassInterface.types
@@ -0,0 +1,19 @@
+=== tests/cases/conformance/classes/classDeclarations/mergedClassInterface.ts ===
+declare class C1 {}
+>C1 : C1
+
+interface C1 {}
+>C1 : C1
+
+interface C2 {}
+>C2 : C2
+
+declare class C2 {}
+>C2 : C2
+
+interface C2 {}
+>C2 : C2
+
+interface C2 {}
+>C2 : C2
+