diff --git a/specs/define-config.spec.ts b/specs/define-config.spec.ts
index 4851c71..dfd30b0 100644
--- a/specs/define-config.spec.ts
+++ b/specs/define-config.spec.ts
@@ -1,76 +1,143 @@
 import { describe, expect, test as spec } from 'bun:test';
+import type { NextConfig } from 'next';
 
 import { defineConfig } from '#src/index.ts';
 
-describe('Next Config', async () => {
-  spec('should return empty config', async () => {
-    expect(defineConfig({}));
+describe('Next Config', () => {
+  spec('should return empty config', () => {
+    const config = defineConfig({});
+
+    expect(config).toMatchObject({});
+    expect(config satisfies NextConfig).toBeDefined();
   });
 
-  spec('should return config', async () => {
-    expect(
-      defineConfig({
-        amp: {
-          canonicalBase: '',
-        },
-        assetPrefix: '',
-        basePath: '',
-        cacheMaxMemorySize: 1200,
-        cacheHandler: '',
-        cleanDistDir: true,
-        compress: true,
-        devIndicators: {
-          buildActivity: true,
-          buildActivityPosition: 'bottom-right',
-        },
-        deploymentId: '',
-        distDir: '',
-        eslint: {
-          dirs: [''],
-          ignoreDuringBuilds: true,
-        },
-        env: {},
-        excludeDefaultMomentLocales: true,
-        generateEtags: false,
-        i18n: {
-          defaultLocale: '',
-          domains: [{ defaultLocale: '', domain: '', http: true, locales: [''] }],
-          localeDetection: false,
-          locales: [],
-        },
-        images: {
-          contentDispositionType: 'attachment',
-          contentSecurityPolicy: '',
-          dangerouslyAllowSVG: false,
-          deviceSizes: [500, 500],
-          disableStaticImages: false,
-          formats: ['image/webp', 'image/avif'],
-          imageSizes: [500, 500],
-          loader: 'akamai',
-          loaderFile: '',
-          minimumCacheTTL: 100,
-          path: '',
-          remotePatterns: [
-            {
-              protocol: 'https',
-              hostname: '',
-              port: '',
-              pathname: '',
-            },
-          ],
-          unoptimized: false,
-        },
-        onDemandEntries: {
-          maxInactiveAge: 100,
-          pagesBufferLength: 100,
-        },
-        pageExtensions: [''],
-        poweredByHeader: false,
-        trailingSlash: true,
-        typescript: { ignoreBuildErrors: false, tsconfigPath: '' },
-        sassOptions: {},
-        useFileSystemPublicRoutes: true,
-      }),
-    );
+  spec('should return config with all properties', () => {
+    const config = defineConfig({
+      amp: {
+        canonicalBase: '',
+      },
+      assetPrefix: '',
+      basePath: '',
+      cacheMaxMemorySize: 1200,
+      cacheHandler: '',
+      cleanDistDir: true,
+      compress: true,
+      devIndicators: {
+        buildActivity: true,
+        buildActivityPosition: 'bottom-right',
+      },
+      deploymentId: '',
+      distDir: '',
+      eslint: {
+        dirs: [''],
+        ignoreDuringBuilds: true,
+      },
+      env: {},
+      excludeDefaultMomentLocales: true,
+      generateEtags: false,
+      i18n: {
+        defaultLocale: '',
+        domains: [{ defaultLocale: '', domain: '', http: true, locales: [''] }],
+        localeDetection: false,
+        locales: [],
+      },
+      images: {
+        contentDispositionType: 'attachment',
+        contentSecurityPolicy: '',
+        dangerouslyAllowSVG: false,
+        deviceSizes: [500, 500],
+        disableStaticImages: false,
+        formats: ['image/webp', 'image/avif'],
+        imageSizes: [500, 500],
+        loader: 'akamai',
+        loaderFile: '',
+        minimumCacheTTL: 100,
+        path: '',
+        remotePatterns: [
+          {
+            protocol: 'https',
+            hostname: '',
+            port: '',
+            pathname: '',
+          },
+        ],
+        unoptimized: false,
+      },
+      onDemandEntries: {
+        maxInactiveAge: 100,
+        pagesBufferLength: 100,
+      },
+      pageExtensions: [''],
+      poweredByHeader: false,
+      trailingSlash: true,
+      typescript: { ignoreBuildErrors: false, tsconfigPath: '' },
+      sassOptions: {},
+      useFileSystemPublicRoutes: true,
+    });
+
+    expect(config).toMatchObject({
+      amp: {
+        canonicalBase: '',
+      },
+      assetPrefix: '',
+      basePath: '',
+      cacheMaxMemorySize: 1200,
+      cacheHandler: '',
+      cleanDistDir: true,
+      compress: true,
+      devIndicators: {
+        buildActivity: true,
+        buildActivityPosition: 'bottom-right',
+      },
+      deploymentId: '',
+      distDir: '',
+      eslint: {
+        dirs: [''],
+        ignoreDuringBuilds: true,
+      },
+      env: {},
+      excludeDefaultMomentLocales: true,
+      generateEtags: false,
+      i18n: {
+        defaultLocale: '',
+        domains: [{ defaultLocale: '', domain: '', http: true, locales: [''] }],
+        localeDetection: false,
+        locales: [],
+      },
+      images: {
+        contentDispositionType: 'attachment',
+        contentSecurityPolicy: '',
+        dangerouslyAllowSVG: false,
+        deviceSizes: [500, 500],
+        disableStaticImages: false,
+        formats: ['image/webp', 'image/avif'],
+        imageSizes: [500, 500],
+        loader: 'akamai',
+        loaderFile: '',
+        minimumCacheTTL: 100,
+        path: '',
+        remotePatterns: [
+          {
+            protocol: 'https',
+            hostname: '',
+            port: '',
+            pathname: '',
+          },
+        ],
+        unoptimized: false,
+      },
+      onDemandEntries: {
+        maxInactiveAge: 100,
+        pagesBufferLength: 100,
+      },
+      pageExtensions: [''],
+      poweredByHeader: false,
+      trailingSlash: true,
+      typescript: { ignoreBuildErrors: false, tsconfigPath: '' },
+      sassOptions: {},
+      useFileSystemPublicRoutes: true,
+    });
+
+    expect(config satisfies NextConfig).toBeDefined();
   });
 });