diff --git a/packages/compiler-cli/test/compliance/BUILD.bazel b/packages/compiler-cli/test/compliance/BUILD.bazel
index d238d225a8..b37fe372c1 100644
--- a/packages/compiler-cli/test/compliance/BUILD.bazel
+++ b/packages/compiler-cli/test/compliance/BUILD.bazel
@@ -22,7 +22,7 @@ jasmine_node_test(
     data = [
         "//packages/compiler-cli/test/ngtsc/fake_core:npm_package",
     ],
-    shard_count = 4,
+    shard_count = 2,
     tags = [
         "ivy-only",
     ],
diff --git a/packages/compiler-cli/test/helpers/index.ts b/packages/compiler-cli/test/helpers/index.ts
index 2c8ece941d..5c504e39cf 100644
--- a/packages/compiler-cli/test/helpers/index.ts
+++ b/packages/compiler-cli/test/helpers/index.ts
@@ -7,3 +7,4 @@
  */
 export {getAngularPackagesFromRunfiles, resolveNpmTreeArtifact} from './src/runfile_helpers';
 export * from './src/mock_file_loading';
+export * from './src/cached_source_files';
diff --git a/packages/compiler-cli/test/helpers/src/cached_source_files.ts b/packages/compiler-cli/test/helpers/src/cached_source_files.ts
new file mode 100644
index 0000000000..64dbd95529
--- /dev/null
+++ b/packages/compiler-cli/test/helpers/src/cached_source_files.ts
@@ -0,0 +1,44 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import * as ts from 'typescript';
+import {basename} from '../../../src/ngtsc/file_system';
+
+// A cache of source files that are typically used across tests and are expensive to parse.
+let sourceFileCache = new Map<string, ts.SourceFile>();
+
+/**
+ * If the `fileName` is determined to benefit from caching across tests, a parsed `ts.SourceFile`
+ * is returned from a shared cache. If caching is not applicable for the requested `fileName`, then
+ * `null` is returned.
+ *
+ * Even if a `ts.SourceFile` already exists for the given `fileName` will the contents be loaded
+ * from disk, such that it can be verified whether the cached `ts.SourceFile` is identical to the
+ * disk contents. If there is a difference, a new `ts.SourceFile` is parsed from the loaded contents
+ * which replaces the prior cache entry.
+ *
+ * @param fileName the path of the file to request a source file for.
+ * @param load a callback to load the contents of the file; this is even called when a cache entry
+ * is available to verify that the cached `ts.SourceFile` corresponds with the contents on disk.
+ */
+export function getCachedSourceFile(
+    fileName: string, load: () => string | undefined): ts.SourceFile|null {
+  if (!/^lib\..+\.d\.ts$/.test(basename(fileName))) {
+    return null;
+  }
+
+  const content = load();
+  if (content === undefined) {
+    return null;
+  }
+  if (!sourceFileCache.has(fileName) || sourceFileCache.get(fileName)!.text !== content) {
+    const sf = ts.createSourceFile(fileName, content, ts.ScriptTarget.ES2015);
+    sourceFileCache.set(fileName, sf);
+  }
+  return sourceFileCache.get(fileName)!;
+}
diff --git a/packages/compiler-cli/test/ngtsc/env.ts b/packages/compiler-cli/test/ngtsc/env.ts
index dcf3a3f25d..869a22e1fc 100644
--- a/packages/compiler-cli/test/ngtsc/env.ts
+++ b/packages/compiler-cli/test/ngtsc/env.ts
@@ -18,6 +18,7 @@ import {IndexedComponent} from '../../src/ngtsc/indexer';
 import {NgtscProgram} from '../../src/ngtsc/program';
 import {LazyRoute} from '../../src/ngtsc/routing';
 import {setWrapHostForTest} from '../../src/transformers/compiler_host';
+import {getCachedSourceFile} from '../helpers';
 
 
 /**
@@ -266,7 +267,17 @@ export class NgtscTestEnvironment {
   }
 }
 
-class AugmentedCompilerHost extends NgtscCompilerHost {
+class NgtscTestCompilerHost extends NgtscCompilerHost {
+  getSourceFile(fileName: string, languageVersion: ts.ScriptTarget): ts.SourceFile|undefined {
+    const cachedSf = getCachedSourceFile(fileName, () => this.readFile(fileName));
+    if (cachedSf !== null) {
+      return cachedSf;
+    }
+    return super.getSourceFile(fileName, languageVersion);
+  }
+}
+
+class AugmentedCompilerHost extends NgtscTestCompilerHost {
   delegate!: ts.CompilerHost;
 }
 
diff --git a/packages/compiler/test/BUILD.bazel b/packages/compiler/test/BUILD.bazel
index ac43c2b336..53444e2738 100644
--- a/packages/compiler/test/BUILD.bazel
+++ b/packages/compiler/test/BUILD.bazel
@@ -29,6 +29,7 @@ ts_library(
         "//packages:types",
         "//packages/compiler",
         "//packages/compiler-cli",
+        "//packages/compiler-cli/test/helpers",
         "@npm//typescript",
     ],
 )
diff --git a/packages/compiler/test/aot/test_util.ts b/packages/compiler/test/aot/test_util.ts
index 1ff49efb4a..006678439a 100644
--- a/packages/compiler/test/aot/test_util.ts
+++ b/packages/compiler/test/aot/test_util.ts
@@ -10,6 +10,7 @@ import {AotCompilerHost, AotCompilerOptions, createAotCompiler, GeneratedFile, t
 import {MetadataBundlerHost} from '@angular/compiler-cli/src/metadata/bundler';
 import {MetadataCollector} from '@angular/compiler-cli/src/metadata/collector';
 import {ModuleMetadata} from '@angular/compiler-cli/src/metadata/index';
+import {getCachedSourceFile} from '@angular/compiler-cli/test/helpers';
 import {newArray} from '@angular/compiler/src/util';
 import * as fs from 'fs';
 import * as path from 'path';
@@ -182,6 +183,10 @@ export class EmittingCompilerHost implements ts.CompilerHost {
       onError?: (message: string) => void): ts.SourceFile {
     const content = this.readFile(fileName);
     if (content) {
+      const cachedSf = getCachedSourceFile(fileName, () => content);
+      if (cachedSf !== null) {
+        return cachedSf;
+      }
       return ts.createSourceFile(fileName, content, languageVersion, /* setParentNodes */ true);
     }
     throw new Error(`File not found '${fileName}'.`);
@@ -316,16 +321,20 @@ export class MockCompilerHost implements ts.CompilerHost {
   // ts.CompilerHost
   getSourceFile(
       fileName: string, languageVersion: ts.ScriptTarget,
-      onError?: (message: string) => void): ts.SourceFile {
+      onError?: (message: string) => void): ts.SourceFile|undefined {
     let result = this.sourceFiles.get(fileName);
     if (!result) {
       const content = this.getFileContent(fileName);
+      const cachedSf = getCachedSourceFile(fileName, () => content);
+      if (cachedSf !== null) {
+        return cachedSf;
+      }
       if (content) {
         result = ts.createSourceFile(fileName, content, languageVersion);
         this.sourceFiles.set(fileName, result);
       }
     }
-    return result!;
+    return result;
   }
 
   getDefaultLibFileName(options: ts.CompilerOptions): string {
@@ -424,7 +433,7 @@ export class MockAotCompilerHost implements AotCompilerHost {
       }
     } else {
       const sf = this.tsHost.getSourceFile(modulePath, ts.ScriptTarget.Latest);
-      const metadata = this.metadataProvider.getMetadata(sf);
+      const metadata = sf && this.metadataProvider.getMetadata(sf);
       return metadata ? [metadata] : [];
     }
     return undefined;