diff --git a/src/testRunner/runner.ts b/src/testRunner/runner.ts
index 3c1a7c5633340..0c5561332d656 100644
--- a/src/testRunner/runner.ts
+++ b/src/testRunner/runner.ts
@@ -6,9 +6,26 @@ namespace Harness {
 
     function runTests(runners: RunnerBase[]) {
         for (let i = iterations; i > 0; i--) {
+            const seen = new Map<string, string>();
+            const dupes: [string, string][] = [];
             for (const runner of runners) {
+                for (const sf of runner.enumerateTestFiles()) {
+                    const full = typeof sf === "string" ? sf : sf.file;
+                    const base = vpath.basename(full).toLowerCase();
+                    // exempt fourslash-fourslash conflicts since they're less likely to emit baselines
+                    if (seen.has(base) && !(/fourslash/.test(seen.get(base)!) && /fourslash/.test(full))) {
+                        dupes.push([seen.get(base)!, full]);
+                    }
+                    else {
+                        seen.set(base, full);
+                    }
+                }
                 runner.initializeTests();
             }
+            if (dupes.length) {
+                throw new Error(`${dupes.length} Tests with duplicate baseline names:
+${JSON.stringify(dupes, undefined, 2)}`);
+            }
         }
     }
 
diff --git a/tests/baselines/reference/abstractProperty.symbols b/tests/baselines/reference/abstractProperty.symbols
deleted file mode 100644
index 3c69af4ffe938..0000000000000
--- a/tests/baselines/reference/abstractProperty.symbols
+++ /dev/null
@@ -1,59 +0,0 @@
-=== tests/cases/compiler/abstractProperty.ts ===
-interface A {
->A : Symbol(A, Decl(abstractProperty.ts, 0, 0))
-
-    prop: string;
->prop : Symbol(A.prop, Decl(abstractProperty.ts, 0, 13))
-
-    raw: string;
->raw : Symbol(A.raw, Decl(abstractProperty.ts, 1, 17))
-
-    m(): void;
->m : Symbol(A.m, Decl(abstractProperty.ts, 2, 16))
-}
-abstract class B implements A {
->B : Symbol(B, Decl(abstractProperty.ts, 4, 1))
->A : Symbol(A, Decl(abstractProperty.ts, 0, 0))
-
-    abstract prop: string;
->prop : Symbol(B.prop, Decl(abstractProperty.ts, 5, 31))
-
-    abstract raw: string;
->raw : Symbol(B.raw, Decl(abstractProperty.ts, 6, 26))
-
-    abstract readonly ro: string;
->ro : Symbol(B.ro, Decl(abstractProperty.ts, 7, 25))
-
-    abstract get readonlyProp(): string;
->readonlyProp : Symbol(B.readonlyProp, Decl(abstractProperty.ts, 8, 33), Decl(abstractProperty.ts, 9, 40))
-
-    abstract set readonlyProp(val: string);
->readonlyProp : Symbol(B.readonlyProp, Decl(abstractProperty.ts, 8, 33), Decl(abstractProperty.ts, 9, 40))
->val : Symbol(val, Decl(abstractProperty.ts, 10, 30))
-
-    abstract m(): void;
->m : Symbol(B.m, Decl(abstractProperty.ts, 10, 43))
-}
-class C extends B {
->C : Symbol(C, Decl(abstractProperty.ts, 12, 1))
->B : Symbol(B, Decl(abstractProperty.ts, 4, 1))
-
-    get prop() { return "foo"; }
->prop : Symbol(C.prop, Decl(abstractProperty.ts, 13, 19), Decl(abstractProperty.ts, 14, 32))
-
-    set prop(v) { }
->prop : Symbol(C.prop, Decl(abstractProperty.ts, 13, 19), Decl(abstractProperty.ts, 14, 32))
->v : Symbol(v, Decl(abstractProperty.ts, 15, 13))
-
-    raw = "edge";
->raw : Symbol(C.raw, Decl(abstractProperty.ts, 15, 19))
-
-    readonly ro = "readonly please";
->ro : Symbol(C.ro, Decl(abstractProperty.ts, 16, 17))
-
-    readonlyProp: string; // don't have to give a value, in fact
->readonlyProp : Symbol(C.readonlyProp, Decl(abstractProperty.ts, 17, 36))
-
-    m() { }
->m : Symbol(C.m, Decl(abstractProperty.ts, 18, 25))
-}
diff --git a/tests/baselines/reference/abstractProperty.js b/tests/baselines/reference/abstractPropertyBasics.js
similarity index 94%
rename from tests/baselines/reference/abstractProperty.js
rename to tests/baselines/reference/abstractPropertyBasics.js
index bfa80a63061ca..b2010c3538162 100644
--- a/tests/baselines/reference/abstractProperty.js
+++ b/tests/baselines/reference/abstractPropertyBasics.js
@@ -1,4 +1,4 @@
-//// [abstractProperty.ts]
+//// [abstractPropertyBasics.ts]
 interface A {
     prop: string;
     raw: string;
@@ -21,7 +21,7 @@ class C extends B {
     m() { }
 }
 
-//// [abstractProperty.js]
+//// [abstractPropertyBasics.js]
 var __extends = (this && this.__extends) || (function () {
     var extendStatics = function (d, b) {
         extendStatics = Object.setPrototypeOf ||
diff --git a/tests/baselines/reference/abstractPropertyBasics.symbols b/tests/baselines/reference/abstractPropertyBasics.symbols
new file mode 100644
index 0000000000000..4d7cd333a96c3
--- /dev/null
+++ b/tests/baselines/reference/abstractPropertyBasics.symbols
@@ -0,0 +1,59 @@
+=== tests/cases/compiler/abstractPropertyBasics.ts ===
+interface A {
+>A : Symbol(A, Decl(abstractPropertyBasics.ts, 0, 0))
+
+    prop: string;
+>prop : Symbol(A.prop, Decl(abstractPropertyBasics.ts, 0, 13))
+
+    raw: string;
+>raw : Symbol(A.raw, Decl(abstractPropertyBasics.ts, 1, 17))
+
+    m(): void;
+>m : Symbol(A.m, Decl(abstractPropertyBasics.ts, 2, 16))
+}
+abstract class B implements A {
+>B : Symbol(B, Decl(abstractPropertyBasics.ts, 4, 1))
+>A : Symbol(A, Decl(abstractPropertyBasics.ts, 0, 0))
+
+    abstract prop: string;
+>prop : Symbol(B.prop, Decl(abstractPropertyBasics.ts, 5, 31))
+
+    abstract raw: string;
+>raw : Symbol(B.raw, Decl(abstractPropertyBasics.ts, 6, 26))
+
+    abstract readonly ro: string;
+>ro : Symbol(B.ro, Decl(abstractPropertyBasics.ts, 7, 25))
+
+    abstract get readonlyProp(): string;
+>readonlyProp : Symbol(B.readonlyProp, Decl(abstractPropertyBasics.ts, 8, 33), Decl(abstractPropertyBasics.ts, 9, 40))
+
+    abstract set readonlyProp(val: string);
+>readonlyProp : Symbol(B.readonlyProp, Decl(abstractPropertyBasics.ts, 8, 33), Decl(abstractPropertyBasics.ts, 9, 40))
+>val : Symbol(val, Decl(abstractPropertyBasics.ts, 10, 30))
+
+    abstract m(): void;
+>m : Symbol(B.m, Decl(abstractPropertyBasics.ts, 10, 43))
+}
+class C extends B {
+>C : Symbol(C, Decl(abstractPropertyBasics.ts, 12, 1))
+>B : Symbol(B, Decl(abstractPropertyBasics.ts, 4, 1))
+
+    get prop() { return "foo"; }
+>prop : Symbol(C.prop, Decl(abstractPropertyBasics.ts, 13, 19), Decl(abstractPropertyBasics.ts, 14, 32))
+
+    set prop(v) { }
+>prop : Symbol(C.prop, Decl(abstractPropertyBasics.ts, 13, 19), Decl(abstractPropertyBasics.ts, 14, 32))
+>v : Symbol(v, Decl(abstractPropertyBasics.ts, 15, 13))
+
+    raw = "edge";
+>raw : Symbol(C.raw, Decl(abstractPropertyBasics.ts, 15, 19))
+
+    readonly ro = "readonly please";
+>ro : Symbol(C.ro, Decl(abstractPropertyBasics.ts, 16, 17))
+
+    readonlyProp: string; // don't have to give a value, in fact
+>readonlyProp : Symbol(C.readonlyProp, Decl(abstractPropertyBasics.ts, 17, 36))
+
+    m() { }
+>m : Symbol(C.m, Decl(abstractPropertyBasics.ts, 18, 25))
+}
diff --git a/tests/baselines/reference/abstractProperty.types b/tests/baselines/reference/abstractPropertyBasics.types
similarity index 88%
rename from tests/baselines/reference/abstractProperty.types
rename to tests/baselines/reference/abstractPropertyBasics.types
index d26af73b9aa7c..123e4041941f6 100644
--- a/tests/baselines/reference/abstractProperty.types
+++ b/tests/baselines/reference/abstractPropertyBasics.types
@@ -1,4 +1,4 @@
-=== tests/cases/compiler/abstractProperty.ts ===
+=== tests/cases/compiler/abstractPropertyBasics.ts ===
 interface A {
     prop: string;
 >prop : string
diff --git a/tests/cases/compiler/abstractProperty.ts b/tests/cases/compiler/abstractPropertyBasics.ts
similarity index 100%
rename from tests/cases/compiler/abstractProperty.ts
rename to tests/cases/compiler/abstractPropertyBasics.ts
diff --git a/tests/cases/fourslash/augmentedTypesClass3.ts b/tests/cases/fourslash/augmentedTypesClass3Fourslash.ts
similarity index 100%
rename from tests/cases/fourslash/augmentedTypesClass3.ts
rename to tests/cases/fourslash/augmentedTypesClass3Fourslash.ts
diff --git a/tests/cases/fourslash/unusedInterfaceInNamespace1.ts b/tests/cases/fourslash/codeFixUnusedInterfaceInNamespace1.ts
similarity index 100%
rename from tests/cases/fourslash/unusedInterfaceInNamespace1.ts
rename to tests/cases/fourslash/codeFixUnusedInterfaceInNamespace1.ts
diff --git a/tests/cases/fourslash/unusedInterfaceInNamespace2.ts b/tests/cases/fourslash/codeFixUnusedInterfaceInNamespace2.ts
similarity index 100%
rename from tests/cases/fourslash/unusedInterfaceInNamespace2.ts
rename to tests/cases/fourslash/codeFixUnusedInterfaceInNamespace2.ts
diff --git a/tests/cases/fourslash/unusedNamespaceInNamespace.ts b/tests/cases/fourslash/codeFixUnusedNamespaceInNamespace.ts
similarity index 100%
rename from tests/cases/fourslash/unusedNamespaceInNamespace.ts
rename to tests/cases/fourslash/codeFixUnusedNamespaceInNamespace.ts
diff --git a/tests/cases/fourslash/commentsEnums.ts b/tests/cases/fourslash/commentsEnumsFourslash.ts
similarity index 100%
rename from tests/cases/fourslash/commentsEnums.ts
rename to tests/cases/fourslash/commentsEnumsFourslash.ts
diff --git a/tests/cases/fourslash/commentsExternalModules.ts b/tests/cases/fourslash/commentsExternalModulesFourslash.ts
similarity index 100%
rename from tests/cases/fourslash/commentsExternalModules.ts
rename to tests/cases/fourslash/commentsExternalModulesFourslash.ts
diff --git a/tests/cases/fourslash/commentsInheritance.ts b/tests/cases/fourslash/commentsInheritanceFourslash.ts
similarity index 100%
rename from tests/cases/fourslash/commentsInheritance.ts
rename to tests/cases/fourslash/commentsInheritanceFourslash.ts
diff --git a/tests/cases/fourslash/commentsInterface.ts b/tests/cases/fourslash/commentsInterfaceFourslash.ts
similarity index 100%
rename from tests/cases/fourslash/commentsInterface.ts
rename to tests/cases/fourslash/commentsInterfaceFourslash.ts
diff --git a/tests/cases/fourslash/commentsModules.ts b/tests/cases/fourslash/commentsModulesFourslash.ts
similarity index 100%
rename from tests/cases/fourslash/commentsModules.ts
rename to tests/cases/fourslash/commentsModulesFourslash.ts
diff --git a/tests/cases/fourslash/commentsMultiModuleMultiFile.ts b/tests/cases/fourslash/commentsMultiModuleMultiFileFourslash.ts
similarity index 100%
rename from tests/cases/fourslash/commentsMultiModuleMultiFile.ts
rename to tests/cases/fourslash/commentsMultiModuleMultiFileFourslash.ts
diff --git a/tests/cases/fourslash/commentsMultiModuleSingleFile.ts b/tests/cases/fourslash/commentsMultiModuleSingleFileFourslash.ts
similarity index 100%
rename from tests/cases/fourslash/commentsMultiModuleSingleFile.ts
rename to tests/cases/fourslash/commentsMultiModuleSingleFileFourslash.ts
diff --git a/tests/cases/fourslash/commentsOverloads.ts b/tests/cases/fourslash/commentsOverloadsFourslash.ts
similarity index 100%
rename from tests/cases/fourslash/commentsOverloads.ts
rename to tests/cases/fourslash/commentsOverloadsFourslash.ts
diff --git a/tests/cases/fourslash/augmentedTypesClass2.ts b/tests/cases/fourslash/completionsAugmentedTypesClass2.ts
similarity index 100%
rename from tests/cases/fourslash/augmentedTypesClass2.ts
rename to tests/cases/fourslash/completionsAugmentedTypesClass2.ts
diff --git a/tests/cases/fourslash/externalModuleRefernceResolutionOrderInImportDeclaration.ts b/tests/cases/fourslash/completionsExternalModuleReferenceResolutionOrderInImportDeclaration.ts
similarity index 100%
rename from tests/cases/fourslash/externalModuleRefernceResolutionOrderInImportDeclaration.ts
rename to tests/cases/fourslash/completionsExternalModuleReferenceResolutionOrderInImportDeclaration.ts
diff --git a/tests/cases/fourslash/genericTypeWithMultipleBases1.ts b/tests/cases/fourslash/completionsGenericTypeWithMultipleBases1.ts
similarity index 100%
rename from tests/cases/fourslash/genericTypeWithMultipleBases1.ts
rename to tests/cases/fourslash/completionsGenericTypeWithMultipleBases1.ts
diff --git a/tests/cases/fourslash/mergedDeclarations1.ts b/tests/cases/fourslash/completionsMergedDeclarations1.ts
similarity index 100%
rename from tests/cases/fourslash/mergedDeclarations1.ts
rename to tests/cases/fourslash/completionsMergedDeclarations1.ts
diff --git a/tests/cases/fourslash/mergedDeclarations2.ts b/tests/cases/fourslash/completionsMergedDeclarations2.ts
similarity index 100%
rename from tests/cases/fourslash/mergedDeclarations2.ts
rename to tests/cases/fourslash/completionsMergedDeclarations2.ts
diff --git a/tests/cases/fourslash/contextualTypingOfArrayLiterals1.ts b/tests/cases/fourslash/contextualTypingOfArrayLiterals.ts
similarity index 100%
rename from tests/cases/fourslash/contextualTypingOfArrayLiterals1.ts
rename to tests/cases/fourslash/contextualTypingOfArrayLiterals.ts
diff --git a/tests/cases/fourslash/jsFileCompilationDuplicateFunctionImplementation.ts b/tests/cases/fourslash/diagnosticsJsFileCompilationDuplicateFunctionImplementation.ts
similarity index 100%
rename from tests/cases/fourslash/jsFileCompilationDuplicateFunctionImplementation.ts
rename to tests/cases/fourslash/diagnosticsJsFileCompilationDuplicateFunctionImplementation.ts
diff --git a/tests/cases/fourslash/multiModuleClodule1.ts b/tests/cases/fourslash/multiModuleClodule.ts
similarity index 100%
rename from tests/cases/fourslash/multiModuleClodule1.ts
rename to tests/cases/fourslash/multiModuleClodule.ts
diff --git a/tests/cases/fourslash/multiModuleFundule1.ts b/tests/cases/fourslash/multiModuleFundule.ts
similarity index 100%
rename from tests/cases/fourslash/multiModuleFundule1.ts
rename to tests/cases/fourslash/multiModuleFundule.ts
diff --git a/tests/cases/fourslash/assignToExistingClass.ts b/tests/cases/fourslash/quickInfoAssignToExistingClass.ts
similarity index 100%
rename from tests/cases/fourslash/assignToExistingClass.ts
rename to tests/cases/fourslash/quickInfoAssignToExistingClass.ts
diff --git a/tests/cases/fourslash/cloduleWithRecursiveReference.ts b/tests/cases/fourslash/quickInfoCloduleWithRecursiveReference.ts
similarity index 100%
rename from tests/cases/fourslash/cloduleWithRecursiveReference.ts
rename to tests/cases/fourslash/quickInfoCloduleWithRecursiveReference.ts
diff --git a/tests/cases/fourslash/contextualTyping.ts b/tests/cases/fourslash/quickInfoContextualTyping.ts
similarity index 100%
rename from tests/cases/fourslash/contextualTyping.ts
rename to tests/cases/fourslash/quickInfoContextualTyping.ts
diff --git a/tests/cases/fourslash/extendArray.ts b/tests/cases/fourslash/quickInfoExtendArray.ts
similarity index 100%
rename from tests/cases/fourslash/extendArray.ts
rename to tests/cases/fourslash/quickInfoExtendArray.ts
diff --git a/tests/cases/fourslash/forIn.ts b/tests/cases/fourslash/quickInfoForIn.ts
similarity index 100%
rename from tests/cases/fourslash/forIn.ts
rename to tests/cases/fourslash/quickInfoForIn.ts
diff --git a/tests/cases/fourslash/genericCombinators2.ts b/tests/cases/fourslash/quickInfoGenericCombinators2.ts
similarity index 100%
rename from tests/cases/fourslash/genericCombinators2.ts
rename to tests/cases/fourslash/quickInfoGenericCombinators2.ts
diff --git a/tests/cases/fourslash/genericTypeArgumentInference1.ts b/tests/cases/fourslash/quickInfoGenericTypeArgumentInference1.ts
similarity index 100%
rename from tests/cases/fourslash/genericTypeArgumentInference1.ts
rename to tests/cases/fourslash/quickInfoGenericTypeArgumentInference1.ts
diff --git a/tests/cases/fourslash/moduleVariables.ts b/tests/cases/fourslash/quickInfoModuleVariables.ts
similarity index 100%
rename from tests/cases/fourslash/moduleVariables.ts
rename to tests/cases/fourslash/quickInfoModuleVariables.ts
diff --git a/tests/cases/fourslash/namedTupleMembers.ts b/tests/cases/fourslash/quickInfoNamedTupleMembers.ts
similarity index 100%
rename from tests/cases/fourslash/namedTupleMembers.ts
rename to tests/cases/fourslash/quickInfoNamedTupleMembers.ts
diff --git a/tests/cases/fourslash/recursiveObjectLiteral.ts b/tests/cases/fourslash/quickInfoRecursiveObjectLiteral.ts
similarity index 100%
rename from tests/cases/fourslash/recursiveObjectLiteral.ts
rename to tests/cases/fourslash/quickInfoRecursiveObjectLiteral.ts
diff --git a/tests/cases/fourslash/staticPrototypePropertyOnClass.ts b/tests/cases/fourslash/quickInfoStaticPrototypePropertyOnClass.ts
similarity index 100%
rename from tests/cases/fourslash/staticPrototypePropertyOnClass.ts
rename to tests/cases/fourslash/quickInfoStaticPrototypePropertyOnClass.ts
diff --git a/tests/cases/fourslash/typeOfThisInStatics.ts b/tests/cases/fourslash/quickInfoTypeOfThisInStatics.ts
similarity index 100%
rename from tests/cases/fourslash/typeOfThisInStatics.ts
rename to tests/cases/fourslash/quickInfoTypeOfThisInStatics.ts
diff --git a/tests/cases/fourslash/typedGenericPrototypeMember.ts b/tests/cases/fourslash/quickInfoTypedGenericPrototypeMember.ts
similarity index 100%
rename from tests/cases/fourslash/typedGenericPrototypeMember.ts
rename to tests/cases/fourslash/quickInfoTypedGenericPrototypeMember.ts
diff --git a/tests/cases/fourslash/untypedModuleImport.ts b/tests/cases/fourslash/quickInfoUntypedModuleImport.ts
similarity index 100%
rename from tests/cases/fourslash/untypedModuleImport.ts
rename to tests/cases/fourslash/quickInfoUntypedModuleImport.ts
diff --git a/tests/cases/fourslash/widenedTypes.ts b/tests/cases/fourslash/quickInfoWidenedTypes.ts
similarity index 100%
rename from tests/cases/fourslash/widenedTypes.ts
rename to tests/cases/fourslash/quickInfoWidenedTypes.ts