Fix duplicate environment entries when withEnvironment sets a key twice

docs/features/containers.md

@@ -83,6 +83,8 @@ const container = await new GenericContainer("alpine")
   .start();
 ```
 
+Calling `withEnvironment` more than once adds to the variables set before. Setting a key again replaces its value.
+
 ### With a platform
 
 ```js

packages/testcontainers/src/generic-container/generic-container.test.ts

@@ -163,6 +163,25 @@ describe("GenericContainer", { timeout: 180_000 }, () => {
     expect(responseBody.customKey).toBe("customValue");
   });
 
+  it("should replace an environment variable that is set twice", async () => {
+    await using container = await new GenericContainer("cristianrgreco/testcontainer:1.1.14")
+      .withEnvironment({ customKey: "first", otherKey: "otherValue" })
+      .withEnvironment({ customKey: "second" })
+      .withExposedPorts(8080)
+      .start();
+
+    const client = await getContainerRuntimeClient();
+    const dockerContainer = client.container.getById(container.getId());
+    const containerInfo = await dockerContainer.inspect();
+    expect(containerInfo.Config.Env.filter((env) => env.startsWith("customKey="))).toEqual(["customKey=second"]);
+    expect(containerInfo.Config.Env).toContain("otherKey=otherValue");
+
+    const url = `http://${container.getHost()}:${container.getMappedPort(8080)}`;
+    const response = await fetch(`${url}/env`);
+    const responseBody = (await response.json()) as { [key: string]: string };
+    expect(responseBody.customKey).toBe("second");
+  });
+
   it("should set command", async () => {
     await using container = await new GenericContainer("cristianrgreco/testcontainer:1.1.14")
       .withCommand(["node", "index.js", "one", "two", "three"])

packages/testcontainers/src/generic-container/generic-container.ts

@@ -348,10 +348,7 @@ export class GenericContainer implements TestContainer {
 
   public withEnvironment(environment: Environment): this {
     this.environment = { ...this.environment, ...environment };
-    this.createOpts.Env = [
-      ...(this.createOpts.Env ?? []),
-      ...Object.entries(environment).map(([key, value]) => `${key}=${value}`),
-    ];
+    this.createOpts.Env = Object.entries(this.environment).map(([key, value]) => `${key}=${value}`);
     return this;
   }