diff --git a/packages/compiler-cli/src/main.ts b/packages/compiler-cli/src/main.ts
index aad3add832..2ec68243c8 100644
--- a/packages/compiler-cli/src/main.ts
+++ b/packages/compiler-cli/src/main.ts
@@ -56,14 +56,33 @@ export function main(
 }
 
 export function mainDiagnosticsForTest(
-    args: string[], config?: NgcParsedConfiguration): ReadonlyArray<ts.Diagnostic|api.Diagnostic> {
+    args: string[], config?: NgcParsedConfiguration,
+    programReuse?: {program: api.Program | undefined},
+    modifiedResourceFiles?: Set<string>| null): ReadonlyArray<ts.Diagnostic|api.Diagnostic> {
   let {project, rootNames, options, errors: configErrors, watch, emitFlags} =
       config || readNgcCommandLineAndConfiguration(args);
   if (configErrors.length) {
     return configErrors;
   }
-  const {diagnostics: compileDiags} = performCompilation(
-      {rootNames, options, emitFlags, emitCallback: createEmitCallback(options)});
+
+  let oldProgram: api.Program|undefined;
+  if (programReuse !== undefined) {
+    oldProgram = programReuse.program;
+  }
+
+  const {diagnostics: compileDiags, program} = performCompilation({
+    rootNames,
+    options,
+    emitFlags,
+    oldProgram,
+    modifiedResourceFiles,
+    emitCallback: createEmitCallback(options),
+  });
+
+  if (programReuse !== undefined) {
+    programReuse.program = program;
+  }
+
   return compileDiags;
 }
 
diff --git a/packages/compiler-cli/test/ngtsc/env.ts b/packages/compiler-cli/test/ngtsc/env.ts
index 0eb391b783..66b242fa7e 100644
--- a/packages/compiler-cli/test/ngtsc/env.ts
+++ b/packages/compiler-cli/test/ngtsc/env.ts
@@ -54,6 +54,7 @@ export class NgtscTestEnvironment {
         "experimentalDecorators": true,
         "skipLibCheck": true,
         "noImplicitAny": true,
+        "noEmitOnError": true,
         "strictNullChecks": true,
         "outDir": "built",
         "baseUrl": ".",
@@ -199,7 +200,23 @@ export class NgtscTestEnvironment {
    */
   driveDiagnostics(): ReadonlyArray<ts.Diagnostic> {
     // ngtsc only produces ts.Diagnostic messages.
-    return mainDiagnosticsForTest(['-p', this.basePath]) as ts.Diagnostic[];
+    let reuseProgram: {program: Program | undefined}|undefined = undefined;
+    if (this.multiCompileHostExt !== null) {
+      reuseProgram = {
+        program: this.oldProgram || undefined,
+      };
+    }
+
+    const diags = mainDiagnosticsForTest(
+        ['-p', this.basePath], undefined, reuseProgram, this.changedResources);
+
+
+    if (this.multiCompileHostExt !== null) {
+      this.oldProgram = reuseProgram !.program !;
+    }
+
+    // In ngtsc, only `ts.Diagnostic`s are produced.
+    return diags as ReadonlyArray<ts.Diagnostic>;
   }
 
   async driveDiagnosticsAsync(): Promise<ReadonlyArray<ts.Diagnostic>> {