diff --git a/packages/language-service/test/diagnostics_spec.ts b/packages/language-service/test/diagnostics_spec.ts
index d0ffac41cf..0b33ae49a6 100644
--- a/packages/language-service/test/diagnostics_spec.ts
+++ b/packages/language-service/test/diagnostics_spec.ts
@@ -24,6 +24,10 @@ import {MockTypescriptHost} from './test_utils';
  * as well.
  */
 
+const EXPRESSION_CASES = '/app/expression-cases.ts';
+const NG_FOR_CASES = '/app/ng-for-cases.ts';
+const NG_IF_CASES = '/app/ng-if-cases.ts';
+
 describe('diagnostics', () => {
   let mockHost: MockTypescriptHost;
   let ngHost: TypeScriptServiceHost;
@@ -57,6 +61,62 @@ describe('diagnostics', () => {
     }
   });
 
+  describe('in expression-cases.ts', () => {
+    it('should report access to an unknown field', () => {
+      const diags = ngLS.getDiagnostics(EXPRESSION_CASES).map(d => d.messageText);
+      expect(diags).toContain(
+          `Identifier 'foo' is not defined. ` +
+          `The component declaration, template variable declarations, ` +
+          `and element references do not contain such a member`);
+    });
+
+    it('should report access to an unknown sub-field', () => {
+      const diags = ngLS.getDiagnostics(EXPRESSION_CASES).map(d => d.messageText);
+      expect(diags).toContain(
+          `Identifier 'nam' is not defined. 'Person' does not contain such a member`);
+    });
+
+    it('should report access to a private member', () => {
+      const diags = ngLS.getDiagnostics(EXPRESSION_CASES).map(d => d.messageText);
+      expect(diags).toContain(`Identifier 'myField' refers to a private member of the component`);
+    });
+
+    it('should report numeric operator errors', () => {
+      const diags = ngLS.getDiagnostics(EXPRESSION_CASES).map(d => d.messageText);
+      expect(diags).toContain('Expected a numeric type');
+    });
+  });
+
+  describe('in ng-for-cases.ts', () => {
+    it('should report an unknown field', () => {
+      const diags = ngLS.getDiagnostics(NG_FOR_CASES).map(d => d.messageText);
+      expect(diags).toContain(
+          `Identifier 'people_1' is not defined. ` +
+          `The component declaration, template variable declarations, ` +
+          `and element references do not contain such a member`);
+    });
+
+    it('should report an unknown context reference', () => {
+      const diags = ngLS.getDiagnostics(NG_FOR_CASES).map(d => d.messageText);
+      expect(diags).toContain(`The template context does not define a member called 'even_1'`);
+    });
+
+    it('should report an unknown value in a key expression', () => {
+      const diags = ngLS.getDiagnostics(NG_FOR_CASES).map(d => d.messageText);
+      expect(diags).toContain(
+          `Identifier 'trackBy_1' is not defined. ` +
+          `The component declaration, template variable declarations, ` +
+          `and element references do not contain such a member`);
+    });
+  });
+
+  describe('in ng-if-cases.ts', () => {
+    it('should report an implicit context reference', () => {
+      const diags = ngLS.getDiagnostics(NG_IF_CASES).map(d => d.messageText);
+      expect(diags).toContain(`The template context does not define a member called 'unknown'`);
+    });
+  });
+
   // #17611
   it('should not report diagnostic on iteration of any', () => {
     const fileName = '/app/test.ng';
@@ -487,7 +547,7 @@ describe('diagnostics', () => {
   describe('templates', () => {
     it('should report errors for invalid templateUrls', () => {
       const fileName = mockHost.addCode(`
-	@Component({
+        @Component({
           templateUrl: '«notAFile»',
         })
         export class MyComponent {}`);
@@ -506,10 +566,10 @@ describe('diagnostics', () => {
 
     it('should not report errors for valid templateUrls', () => {
       const fileName = mockHost.addCode(`
-	@Component({
+        @Component({
           templateUrl: './test.ng',
-	})
-	export class MyComponent {}`);
+        })
+        export class MyComponent {}`);
 
       const diagnostics = ngLS.getDiagnostics(fileName) !;
       const urlDiagnostic =
diff --git a/packages/language-service/test/language_service_spec.ts b/packages/language-service/test/language_service_spec.ts
index 1898a22038..66bc5b9634 100644
--- a/packages/language-service/test/language_service_spec.ts
+++ b/packages/language-service/test/language_service_spec.ts
@@ -14,21 +14,31 @@ import {TypeScriptServiceHost} from '../src/typescript_host';
 import {MockTypescriptHost} from './test_utils';
 
 describe('service without angular', () => {
-  let mockHost = new MockTypescriptHost(['/app/main.ts', '/app/parsing-cases.ts']);
-  mockHost.forgetAngular();
-  let service = ts.createLanguageService(mockHost);
-  let ngHost = new TypeScriptServiceHost(mockHost, service);
-  let ngService = createLanguageService(ngHost);
+  const mockHost = new MockTypescriptHost(['/app/main.ts', '/app/parsing-cases.ts']);
+  const service = ts.createLanguageService(mockHost);
+  const ngHost = new TypeScriptServiceHost(mockHost, service);
+  const ngService = createLanguageService(ngHost);
   const fileName = '/app/test.ng';
   const position = mockHost.getLocationMarkerFor(fileName, 'h1-content').start;
 
+  beforeEach(() => { mockHost.reset(); });
+
   it('should not crash a get template references',
-     () => expect(() => ngService.getTemplateReferences()));
+     () => { expect(() => ngService.getTemplateReferences()).not.toThrow(); });
   it('should not crash a get diagnostics',
-     () => expect(() => ngService.getDiagnostics(fileName)).not.toThrow());
+     () => { expect(() => ngService.getDiagnostics(fileName)).not.toThrow(); });
+
   it('should not crash a completion',
-     () => expect(() => ngService.getCompletionsAt(fileName, position)).not.toThrow());
+     () => { expect(() => ngService.getCompletionsAt(fileName, position)).not.toThrow(); });
+
   it('should not crash a get definition',
-     () => expect(() => ngService.getDefinitionAt(fileName, position)).not.toThrow());
-  it('should not crash a hover', () => expect(() => ngService.getHoverAt(fileName, position)));
+     () => { expect(() => ngService.getDefinitionAt(fileName, position)).not.toThrow(); });
+
+  it('should not crash a hover',
+     () => { expect(() => ngService.getHoverAt(fileName, position)).not.toThrow(); });
+
+  it('should not crash with an incomplete class', () => {
+    mockHost.addCode('\nexport class');
+    expect(() => ngHost.getAnalyzedModules()).not.toThrow();
+  });
 });
diff --git a/packages/language-service/test/ts_plugin_spec.ts b/packages/language-service/test/ts_plugin_spec.ts
index 781db1a9fa..fbe2063a8f 100644
--- a/packages/language-service/test/ts_plugin_spec.ts
+++ b/packages/language-service/test/ts_plugin_spec.ts
@@ -139,51 +139,6 @@ describe('plugin', () => {
   });
 
   describe('for semantic errors', () => {
-    it('should report access to an unknown field', () => {
-      expectSemanticError(
-          '/app/expression-cases.ts', 'foo',
-          'Identifier \'foo\' is not defined. The component declaration, template variable declarations, and element references do not contain such a member');
-    });
-    it('should report access to an unknown sub-field', () => {
-      expectSemanticError(
-          '/app/expression-cases.ts', 'nam',
-          'Identifier \'nam\' is not defined. \'Person\' does not contain such a member');
-    });
-    it('should report access to a private member', () => {
-      expectSemanticError(
-          '/app/expression-cases.ts', 'myField',
-          'Identifier \'myField\' refers to a private member of the component');
-    });
-    it('should report numeric operator errors', () => {
-      expectSemanticError('/app/expression-cases.ts', 'mod', 'Expected a numeric type');
-    });
-    describe('in ngFor', () => {
-      function expectError(locationMarker: string, message: string) {
-        expectSemanticError('/app/ng-for-cases.ts', locationMarker, message);
-      }
-      it('should report an unknown field', () => {
-        expectError(
-            'people_1',
-            'Identifier \'people_1\' is not defined. The component declaration, template variable declarations, and element references do not contain such a member');
-      });
-      it('should report an unknown context reference', () => {
-        expectError('even_1', `The template context does not define a member called 'even_1'`);
-      });
-      it('should report an unknown value in a key expression', () => {
-        expectError(
-            'trackBy_1',
-            'Identifier \'trackBy_1\' is not defined. The component declaration, template variable declarations, and element references do not contain such a member');
-      });
-    });
-    describe('in ngIf', () => {
-      function expectError(locationMarker: string, message: string) {
-        expectSemanticError('/app/ng-if-cases.ts', locationMarker, message);
-      }
-      it('should report an implicit context reference', () => {
-        expectError('implicit', `The template context does not define a member called 'unknown'`);
-      });
-    });
-
     describe(`with config 'angularOnly = true`, () => {
       const ngLS = createPlugin(service, mockHost, {angularOnly: true});
       it('should not report template errors on TOH', () => {
@@ -236,21 +191,6 @@ describe('plugin', () => {
         locationMarker, plugin.getCompletionsAtPosition(fileName, marker.start, undefined) !,
         ...names);
   }
-
-  function expectSemanticError(fileName: string, locationMarker: string, message: string) {
-    const marker = mockHost.getLocationMarkerFor(fileName, locationMarker);
-    const errors = plugin.getSemanticDiagnostics(fileName);
-    for (const error of errors) {
-      if (error.messageText.toString().indexOf(message) >= 0) {
-        expect(error.start).toEqual(marker.start);
-        expect(error.length).toEqual(marker.length);
-        return;
-      }
-    }
-    throw new Error(`Expected error messages to contain ${message}, in messages:\n  ${errors
-                        .map(e => e.messageText.toString())
-                        .join(',\n  ')}`);
-  }
 });