diff --git a/.github/workflows/next-drupal.yml b/.github/workflows/next-drupal.yml
index 477cd61e..dbda773a 100644
--- a/.github/workflows/next-drupal.yml
+++ b/.github/workflows/next-drupal.yml
@@ -14,7 +14,9 @@ jobs:
       - name: Install modules
         run: yarn
       - name: Run tests
-        run: yarn test packages/next-drupal
+        run: |
+          yarn test packages/next-drupal
+          yarn test:build
         env:
           DRUPAL_BASE_URL: ${{ secrets.DRUPAL_BASE_URL }}
           DRUPAL_USERNAME: ${{ secrets.DRUPAL_USERNAME }}
diff --git a/jest.config.ts b/jest.config.ts
index 3ab4fbfb..4ead956b 100644
--- a/jest.config.ts
+++ b/jest.config.ts
@@ -1,11 +1,27 @@
 import type { Config } from "@jest/types"
 
+let mappedModule: string
+switch (process.env.TEST_ENV) {
+  // Depending on the TEST_ENV, we test the src or one of the builds.
+  case "esm":
+    mappedModule = "<rootDir>/packages/next-drupal/dist/index.modern.js"
+    break
+  case "cjs":
+    mappedModule = "<rootDir>/packages/next-drupal/dist/index.cjs"
+    break
+  default:
+    mappedModule = "<rootDir>/packages/next-drupal/src/index.ts"
+}
+
 const config: Config.InitialOptions = {
   preset: "ts-jest/presets/js-with-ts",
   testEnvironment: "node",
   setupFiles: ["dotenv/config"],
   setupFilesAfterEnv: ["<rootDir>/jest.setup.ts"],
   testMatch: ["**/tests/**/*.test.{ts,tsx}"],
+  moduleNameMapper: {
+    "^next-drupal-build-testing$": mappedModule,
+  },
   testPathIgnorePatterns: [
     "/node_modules/",
     "/fixtures/",
diff --git a/package.json b/package.json
index 2beab210..96e43fa7 100644
--- a/package.json
+++ b/package.json
@@ -27,6 +27,9 @@
     "cy:open": "turbo run cy:open --parallel",
     "test": "jest",
     "pretest": "yarn format:check && yarn lint",
+    "test:build": "yarn prepare && yarn test:build:esm && yarn test:build:cjs",
+    "test:build:esm": "TEST_ENV=esm jest",
+    "test:build:cjs": "TEST_ENV=cjs jest",
     "test:e2e": "turbo run test:e2e --parallel",
     "test:e2e:ci": "turbo run test:e2e:ci --parallel"
   },
diff --git a/packages/next-drupal/tests/client.test.ts b/packages/next-drupal/tests/client.test.ts
index 011bfd35..50a7ccc1 100644
--- a/packages/next-drupal/tests/client.test.ts
+++ b/packages/next-drupal/tests/client.test.ts
@@ -1,6 +1,6 @@
 import { expect } from "@jest/globals"
 import { GetStaticPropsContext } from "next"
-import { DrupalClient } from "../src/client"
+import { DrupalClient } from "next-drupal-build-testing"
 import type {
   Serializer,
   DrupalNode,
diff --git a/packages/next-drupal/tests/crud.test.ts b/packages/next-drupal/tests/crud.test.ts
index ed9a00b2..5dac72df 100644
--- a/packages/next-drupal/tests/crud.test.ts
+++ b/packages/next-drupal/tests/crud.test.ts
@@ -1,5 +1,5 @@
 import { expect } from "@jest/globals"
-import { DrupalClient } from "../src/client"
+import { DrupalClient } from "next-drupal-build-testing"
 import type { DrupalNode } from "../src/types"
 import { BASE_URL, deleteTestNodes, toggleDrupalModule } from "./utils"
 
diff --git a/packages/next-drupal/tests/utils.ts b/packages/next-drupal/tests/utils.ts
index 762eb6ba..6def8dc0 100644
--- a/packages/next-drupal/tests/utils.ts
+++ b/packages/next-drupal/tests/utils.ts
@@ -1,4 +1,4 @@
-import { DrupalClient } from "../src/client"
+import { DrupalClient } from "next-drupal-build-testing"
 
 // Run all tests against this env until we configure CI to setup a Drupal instance.
 // TODO: Bootstrap and expose the /drupal env for testing.