diff --git a/tests/config/loader.test.js b/tests/config/loader.test.js
new file mode 100644
index 0000000..8860731
--- /dev/null
+++ b/tests/config/loader.test.js
@@ -0,0 +1,92 @@
+import fs from "fs";
+import os from "os";
+import path from "path";
+import { loadConfig } from "../../src/config/loader.js";
+
+describe("loadConfig", () => {
+  let originalCwd;
+  let tempDir;
+
+  beforeEach(() => {
+    originalCwd = process.cwd();
+    tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "apidrift-loader-"));
+    process.chdir(tempDir);
+    delete process.env.STAGING_TOKEN;
+  });
+
+  afterEach(() => {
+    process.chdir(originalCwd);
+    fs.rmSync(tempDir, { recursive: true, force: true });
+    delete process.env.STAGING_TOKEN;
+  });
+
+  test("returns default config when apidrift.config.json is missing", () => {
+    expect(loadConfig()).toEqual({
+      environments: {},
+      endpoints: [],
+      discovery: "heuristic",
+    });
+  });
+
+  test("interpolates environment variables from config placeholders", () => {
+    process.env.STAGING_TOKEN = "staging-secret-token";
+
+    fs.writeFileSync(
+      "apidrift.config.json",
+      JSON.stringify({
+        environments: {
+          staging: {
+            baseUrl: "https://staging.example.com",
+            headers: {
+              authorization: "Bearer ${STAGING_TOKEN}",
+            },
+          },
+        },
+        endpoints: ["/users"],
+        discovery: "openapi",
+      }),
+    );
+
+    expect(loadConfig()).toEqual({
+      environments: {
+        staging: {
+          baseUrl: "https://staging.example.com",
+          headers: {
+            authorization: "Bearer staging-secret-token",
+          },
+        },
+      },
+      endpoints: ["/users"],
+      discovery: "openapi",
+    });
+  });
+
+  test("replaces missing environment variables with an empty string", () => {
+    fs.writeFileSync(
+      "apidrift.config.json",
+      JSON.stringify({
+        environments: {
+          staging: {
+            headers: {
+              authorization: "Bearer ${STAGING_TOKEN}",
+            },
+          },
+        },
+        endpoints: [],
+        discovery: "heuristic",
+      }),
+    );
+
+    expect(loadConfig()).toEqual({
+      environments: {
+        staging: {
+          headers: {
+            authorization: "Bearer ",
+          },
+        },
+      },
+      endpoints: [],
+      discovery: "heuristic",
+    });
+  });
+});