diff --git a/packages/config-loader/package.json b/packages/config-loader/package.json
index 92d20ef1e7..592b8eefb3 100644
--- a/packages/config-loader/package.json
+++ b/packages/config-loader/package.json
@@ -37,8 +37,10 @@
   },
   "devDependencies": {
     "@types/jest": "^26.0.7",
+    "@types/mock-fs": "^4.10.0",
     "@types/node": "^12.0.0",
-    "@types/yup": "^0.28.2"
+    "@types/yup": "^0.28.2",
+    "mock-fs": "^4.13.0"
   },
   "files": [
     "dist"
diff --git a/packages/config-loader/src/lib/resolver.test.ts b/packages/config-loader/src/lib/resolver.test.ts
index c804a6cef3..9fd71f2486 100644
--- a/packages/config-loader/src/lib/resolver.test.ts
+++ b/packages/config-loader/src/lib/resolver.test.ts
@@ -14,46 +14,48 @@
  * limitations under the License.
  */
 
-const pathExists = jest.fn();
-
-jest.mock('fs-extra', () => ({ pathExists }));
-
+import mockFs from 'mock-fs';
 import { resolveStaticConfig } from './resolver';
 
+function normalizePaths(paths: string[]) {
+  return paths.map(p =>
+    p
+      .replace(/^[a-z]:/i, '')
+      .split('\\')
+      .join('/'),
+  );
+}
+
 describe('resolveStaticConfig', () => {
   afterEach(() => {
-    jest.resetAllMocks();
+    mockFs.restore();
   });
 
   it('should resolve no files for empty roots', async () => {
+    mockFs({});
     const resolved = await resolveStaticConfig({
       env: 'development',
       rootPaths: [],
     });
 
-    expect(resolved).toEqual([]);
-    expect(pathExists).not.toHaveBeenCalled();
+    expect(normalizePaths(resolved)).toEqual([]);
   });
 
   it('should resolve a single app-config', async () => {
-    pathExists.mockImplementation(async (path: string) =>
-      ['/repo/app-config.yaml'].includes(path),
-    );
+    mockFs({ '/repo/app-config.yaml': '' });
     const resolved = await resolveStaticConfig({
       env: 'development',
       rootPaths: ['/repo'],
     });
 
-    expect(resolved).toEqual(['/repo/app-config.yaml']);
-    expect(pathExists).toHaveBeenCalledTimes(4);
+    expect(normalizePaths(resolved)).toEqual(['/repo/app-config.yaml']);
   });
 
   it('should resolve a app-configs in different directories', async () => {
-    pathExists.mockImplementation(async (path: string) =>
-      ['/repo/app-config.yaml', '/repo/packages/a/app-config.yaml'].includes(
-        path,
-      ),
-    );
+    mockFs({
+      '/repo/app-config.yaml': '',
+      '/repo/packages/a/app-config.yaml': '',
+    });
     const resolved = await resolveStaticConfig({
       env: 'development',
       rootPaths: [
@@ -64,53 +66,54 @@ describe('resolveStaticConfig', () => {
       ],
     });
 
-    expect(resolved).toEqual([
+    expect(normalizePaths(resolved)).toEqual([
       '/repo/app-config.yaml',
       '/repo/packages/a/app-config.yaml',
     ]);
-    expect(pathExists).toHaveBeenCalledTimes(16);
   });
 
   it('should resolve env and local configs', async () => {
-    pathExists.mockImplementation(async (path: string) =>
-      [
-        '/repo/app-config.yaml',
-        '/repo/app-config.local.yaml',
-        '/repo/app-config.production.yaml',
-        '/repo/app-config.production.local.yaml',
-        '/repo/app-config.development.local.yaml',
-        '/repo/packages/a/app-config.development.yaml',
-        '/repo/packages/a/app-config.local.yaml',
-      ].includes(path),
-    );
+    mockFs({
+      '/repo/app-config.yaml': '',
+      '/repo/app-config.local.yaml': '',
+      '/repo/app-config.production.yaml': '',
+      '/repo/app-config.production.local.yaml': '',
+      '/repo/app-config.development.local.yaml': '',
+      '/repo/packages/a/app-config.development.yaml': '',
+      '/repo/packages/a/app-config.local.yaml': '',
+    });
     const resolved = await resolveStaticConfig({
       env: 'development',
       rootPaths: ['/repo', '/repo/packages/a'],
     });
 
-    expect(resolved).toEqual([
+    expect(normalizePaths(resolved)).toEqual([
       '/repo/app-config.yaml',
       '/repo/app-config.local.yaml',
       '/repo/app-config.development.local.yaml',
       '/repo/packages/a/app-config.local.yaml',
       '/repo/packages/a/app-config.development.yaml',
     ]);
-    expect(pathExists).toHaveBeenCalledTimes(8);
   });
 
   it('resolves suffixed configs in the correct order', async () => {
-    pathExists.mockImplementation(async () => true);
+    mockFs({
+      '/repo/app-config.yaml': '',
+      '/repo/app-config.local.yaml': '',
+      '/repo/app-config.production.yaml': '',
+      '/repo/app-config.production.local.yaml': '',
+    });
+
     const resolved = await resolveStaticConfig({
       env: 'production',
       rootPaths: ['/repo'],
     });
 
-    expect(resolved).toEqual([
+    expect(normalizePaths(resolved)).toEqual([
       '/repo/app-config.yaml',
       '/repo/app-config.local.yaml',
       '/repo/app-config.production.yaml',
       '/repo/app-config.production.local.yaml',
     ]);
-    expect(pathExists).toHaveBeenCalledTimes(4);
   });
 });
diff --git a/packages/config-loader/src/loader.test.ts b/packages/config-loader/src/loader.test.ts
index 4a7c9f238c..a7547ee8fb 100644
--- a/packages/config-loader/src/loader.test.ts
+++ b/packages/config-loader/src/loader.test.ts
@@ -15,45 +15,30 @@
  */
 
 import { loadConfig } from './loader';
-
-jest.mock('fs-extra', () => {
-  const mockFiles: { [path in string]: string } = {
-    '/root/app-config.yaml': `
-      app:
-        title: Example App
-        sessionKey:
-          $secret:
-            file: secrets/session-key.txt
-    `,
-    '/root/app-config.development.yaml': `
-      app:
-        sessionKey: development-key
-    `,
-    '/root/secrets/session-key.txt': 'abc123',
-    '/secret-port/app-config.yaml': `
-      backend:
-        listen:
-          port:
-            $secret:
-              file: secrets/port.txt
-    `,
-    '/secret-port/secrets/port.txt': '12345',
-  };
-
-  return {
-    async readFile(path: string) {
-      if (path in mockFiles) {
-        return mockFiles[path];
-      }
-      throw new Error(`File not found, ${path}`);
-    },
-    async pathExists(path: string) {
-      return path in mockFiles;
-    },
-  };
-});
+import mockFs from 'mock-fs';
 
 describe('loadConfig', () => {
+  beforeAll(() => {
+    mockFs({
+      '/root/app-config.yaml': `
+        app:
+          title: Example App
+          sessionKey:
+            $secret:
+              file: secrets/session-key.txt
+      `,
+      '/root/app-config.development.yaml': `
+        app:
+          sessionKey: development-key
+      `,
+      '/root/secrets/session-key.txt': 'abc123',
+    });
+  });
+
+  afterAll(() => {
+    mockFs.restore();
+  });
+
   it('loads config without secrets', async () => {
     await expect(
       loadConfig({
diff --git a/yarn.lock b/yarn.lock
index 1853f23f7f..d241aff898 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4460,6 +4460,13 @@
   dependencies:
     "@types/node" "*"
 
+"@types/mock-fs@^4.10.0":
+  version "4.10.0"
+  resolved "https://registry.npmjs.org/@types/mock-fs/-/mock-fs-4.10.0.tgz#460061b186993d76856f669d5317cda8a007c24b"
+  integrity sha512-FQ5alSzmHMmliqcL36JqIA4Yyn9jyJKvRSGV3mvPh108VFatX7naJDzSG4fnFQNZFq9dIx0Dzoe6ddflMB2Xkg==
+  dependencies:
+    "@types/node" "*"
+
 "@types/morgan@^1.9.0":
   version "1.9.1"
   resolved "https://registry.npmjs.org/@types/morgan/-/morgan-1.9.1.tgz#6457872df95647c1dbc6b3741e8146b71ece74bf"
@@ -14682,6 +14689,11 @@ mkdirp@^0.5.0, mkdirp@^0.5.1, mkdirp@^0.5.3, mkdirp@^0.5.4, mkdirp@^0.5.5, mkdir
   dependencies:
     minimist "^1.2.5"
 
+mock-fs@^4.13.0:
+  version "4.13.0"
+  resolved "https://registry.npmjs.org/mock-fs/-/mock-fs-4.13.0.tgz#31c02263673ec3789f90eb7b6963676aa407a598"
+  integrity sha512-DD0vOdofJdoaRNtnWcrXe6RQbpHkPPmtqGq14uRX0F8ZKJ5nv89CVTYl/BZdppDxBDaV0hl75htg3abpEWlPZA==
+
 modify-values@^1.0.0:
   version "1.0.1"
   resolved "https://registry.npmjs.org/modify-values/-/modify-values-1.0.1.tgz#b3939fa605546474e3e3e3c63d64bd43b4ee6022"