diff --git a/src/__tests__/index.spec.ts b/src/__tests__/index.spec.ts
index 0ac98b24f8..d4dbd6e5d7 100644
--- a/src/__tests__/index.spec.ts
+++ b/src/__tests__/index.spec.ts
@@ -10,6 +10,7 @@ describe('NgJestTransformer', () => {
       () => {
         const obj1 = {
           config: { cwd: process.cwd(), extensionsToTreatAsEsm: [], globals: {}, testMatch: [], testRegex: [] },
+          cacheFS: new Map(),
         };
         const obj2 = { ...obj1, config: { ...obj1.config, globals: {} } };
         // eslint-disable-next-line
@@ -24,6 +25,7 @@ describe('NgJestTransformer', () => {
     test('should return the same config set for same values with jest config objects', () => {
       const obj1 = {
         config: { cwd: process.cwd(), extensionsToTreatAsEsm: [], globals: {}, testMatch: [], testRegex: [] },
+        cacheFS: new Map(),
       };
       const obj2 = { ...obj1 };
       // eslint-disable-next-line
@@ -84,7 +86,7 @@ describe('NgJestTransformer', () => {
       const input = {
         fileContent: 'const foo = 1',
         // eslint-disable-next-line
-        options: { config: { ...jestCfg } as any, instrument: false, rootDir: '/foo' },
+        options: { config: { ...jestCfg } as any, instrument: false, rootDir: '/foo', cacheFS: new Map(), },
       };
       // eslint-disable-next-line
       const ngJestTransformer = require('../');
@@ -121,7 +123,7 @@ describe('NgJestTransformer', () => {
       };
       const input = {
         // eslint-disable-next-line
-        options: { config: { ...jestCfg } as any, instrument: false, rootDir: '/foo' },
+        options: { config: { ...jestCfg } as any, instrument: false, rootDir: '/foo', cacheFS: new Map(), },
       };
       // eslint-disable-next-line
       const ngJestTransformer = require('../');
diff --git a/src/__tests__/ng-jest-compiler.spec.ts b/src/__tests__/ng-jest-compiler.spec.ts
index a83e6a4fe7..bb3fecc5d1 100644
--- a/src/__tests__/ng-jest-compiler.spec.ts
+++ b/src/__tests__/ng-jest-compiler.spec.ts
@@ -45,7 +45,7 @@ describe('NgJestCompiler', () => {
     // Isolated modules true doesn't have downlevel ctor so this snapshot test should produce different input than with Program
     test('should return result', () => {
       const fileName = join(__dirname, '__mocks__', 'foo.service.ts');
-      const compiler = new NgJestCompiler(ngJestConfig);
+      const compiler = new NgJestCompiler(ngJestConfig, new Map());
 
       // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
       compiler.getCompiledOutput(fileName, readFileSync(fileName, 'utf-8'))!;
@@ -60,7 +60,7 @@ describe('NgJestCompiler', () => {
         ...ngJestConfig.parsedTsConfig,
         rootNames: [fileName],
       };
-      const compiler = new NgJestCompiler(ngJestConfig);
+      const compiler = new NgJestCompiler(ngJestConfig, new Map());
 
       // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
       compiler.getCompiledOutput(fileName, readFileSync(fileName, 'utf-8'))!;
@@ -79,7 +79,7 @@ describe('NgJestCompiler', () => {
         ...ngJestConfig.parsedTsConfig,
         rootNames: [],
       };
-      const compiler = new NgJestCompiler(ngJestConfig);
+      const compiler = new NgJestCompiler(ngJestConfig, new Map());
 
       // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
       const emittedResult = compiler.getCompiledOutput(fileName, readFileSync(fileName, 'utf-8'))!;
@@ -94,7 +94,7 @@ describe('NgJestCompiler', () => {
         ...ngJestConfig.parsedTsConfig,
         rootNames: [fileName],
       };
-      const compiler = new NgJestCompiler(ngJestConfig);
+      const compiler = new NgJestCompiler(ngJestConfig, new Map());
 
       // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
       const emittedResult = compiler.getCompiledOutput(fileName, readFileSync(fileName, 'utf-8'))!;
@@ -109,7 +109,7 @@ describe('NgJestCompiler', () => {
         ...ngJestConfig.parsedTsConfig,
         rootNames: [],
       };
-      const compiler = new NgJestCompiler(ngJestConfig);
+      const compiler = new NgJestCompiler(ngJestConfig, new Map());
 
       expect(() =>
         compiler.getCompiledOutput('foo.ts', readFileSync(fileName, 'utf-8')),
@@ -122,7 +122,7 @@ describe('NgJestCompiler', () => {
         ...ngJestConfig.parsedTsConfig,
         rootNames: [fileName],
       };
-      const compiler = new NgJestCompiler(ngJestConfig);
+      const compiler = new NgJestCompiler(ngJestConfig, new Map());
 
       expect(() =>
         compiler.getCompiledOutput(fileName, readFileSync(fileName, 'utf-8')),
@@ -136,7 +136,7 @@ describe('NgJestCompiler', () => {
         rootNames: [fileName],
       };
       ngJestConfig.shouldReportDiagnostics = jest.fn().mockReturnValueOnce(false);
-      const compiler = new NgJestCompiler(ngJestConfig);
+      const compiler = new NgJestCompiler(ngJestConfig, new Map());
 
       expect(() => compiler.getCompiledOutput(fileName, readFileSync(fileName, 'utf-8'))).not.toThrowError();
     });
@@ -148,7 +148,7 @@ describe('NgJestCompiler', () => {
         ...ngJestConfig.parsedTsConfig,
         rootNames: [fileName],
       };
-      const compiler = new NgJestCompiler(ngJestConfig);
+      const compiler = new NgJestCompiler(ngJestConfig, new Map());
 
       // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
       const emittedResult = compiler.getCompiledOutput(fileName, readFileSync(fileName, 'utf-8'))!;
diff --git a/src/compiler/compiler-host.ts b/src/compiler/compiler-host.ts
index 5fe4027e02..e5af60ad7e 100644
--- a/src/compiler/compiler-host.ts
+++ b/src/compiler/compiler-host.ts
@@ -9,12 +9,11 @@ import type { CompilerOptions } from '@angular/compiler-cli';
 
 export class NgJestCompilerHost implements ts.CompilerHost {
   private readonly _sourceFileCache: Map<string, ts.SourceFile> = new Map<string, ts.SourceFile>();
-  private readonly _memoryHost: Map<string, string | undefined> = new Map<string, string | undefined>();
   private readonly _emittedResult: [string, string] = ['', ''];
   private readonly _ts: TTypeScript;
   private readonly _moduleResolutionCache: ts.ModuleResolutionCache;
 
-  constructor(private logger: Logger, private ngJestCfg: NgJestConfig) {
+  constructor(readonly logger: Logger, readonly ngJestCfg: NgJestConfig, readonly jestCacheFS: Map<string, string>) {
     this._ts = this.ngJestCfg.compilerModule;
     this._moduleResolutionCache = this._ts.createModuleResolutionCache(this.ngJestCfg.cwd, (x) => x);
   }
@@ -24,10 +23,10 @@ export class NgJestCompilerHost implements ts.CompilerHost {
   }
 
   updateMemoryHost(fileName: string, fileContent: string): void {
-    const previousContents = this._memoryHost.get(fileName);
+    const previousContents = this.jestCacheFS.get(fileName);
     const contentsChanged = previousContents !== fileContent;
     if (contentsChanged) {
-      this._memoryHost.set(fileName, fileContent);
+      this.jestCacheFS.set(fileName, fileContent);
     }
   }
 
@@ -92,15 +91,18 @@ export class NgJestCompilerHost implements ts.CompilerHost {
 
   readFile(fileName: string): string | undefined {
     const normalizedFileName = normalize(fileName);
-    let fileContent = this._memoryHost.get(normalizedFileName);
-    if (!fileContent) {
-      this.logger.debug(
-        { fileName: normalizedFileName },
-        'readFile: file does not exist in memory cache, read file with file system',
-      );
+    let fileContent = this.jestCacheFS.get(normalizedFileName);
 
+    this.logger.debug(
+      { fileName: normalizedFileName },
+      'readFile: file does not exist in memory cache, read file with file system',
+    );
+
+    if (!fileContent) {
       fileContent = this._ts.sys.readFile(normalizedFileName) ?? undefined;
-      this._memoryHost.set(normalizedFileName, fileContent);
+      if (fileContent) {
+        this.jestCacheFS.set(normalizedFileName, fileContent);
+      }
     }
 
     return fileContent;
diff --git a/src/compiler/ng-jest-compiler.ts b/src/compiler/ng-jest-compiler.ts
index 3ac8fa3410..6431fc2dc5 100644
--- a/src/compiler/ng-jest-compiler.ts
+++ b/src/compiler/ng-jest-compiler.ts
@@ -18,7 +18,7 @@ export class NgJestCompiler implements CompilerInstance {
   private readonly _logger: Logger;
   private readonly _ts: TTypeScript;
 
-  constructor(readonly ngJestConfig: NgJestConfig) {
+  constructor(readonly ngJestConfig: NgJestConfig, readonly jestCacheFS: Map<string, string>) {
     this._logger = this.ngJestConfig.logger;
     this._ts = this.ngJestConfig.compilerModule;
     this._setupOptions(this.ngJestConfig);
@@ -117,7 +117,7 @@ export class NgJestCompiler implements CompilerInstance {
         '_setupOptions: creating Compiler Host using @angular/compiler-cli createCompilerHost',
       );
 
-      this._tsHost = new NgJestCompilerHost(this._logger, this.ngJestConfig);
+      this._tsHost = new NgJestCompilerHost(this._logger, this.ngJestConfig, this.jestCacheFS);
       this._compilerHost = createCompilerHost({
         options: this._compilerOptions,
         tsHost: this._tsHost,
diff --git a/src/index.ts b/src/index.ts
index abc2125923..581589c548 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -74,7 +74,7 @@ class NgJestTransformer extends TsJestTransformer {
         this._logger.info('no matching config-set found, creating a new one');
 
         ngJestConfig = new NgJestConfig(jestConfig);
-        this._compiler = new NgJestCompiler(ngJestConfig);
+        this._compiler = new NgJestCompiler(ngJestConfig, transformOptions.cacheFS);
         this._transformCfgStr = new JsonableValue({
           ...jestConfig,
           ...ngJestConfig.parsedTsConfig,