Add e2e tests to verify existing proxy is being respected.

test/e2e/Dockerfile

@@ -29,6 +29,9 @@ ARG PNPM_VERSION=latest
 SHELL ["/bin/bash", "-c"]
 ENV BASH_ENV=~/.bashrc
 
+# Install a proxy
+RUN apt-get update && apt-get install tinyproxy -y
+
 # Install zsh
 RUN sh -c "$(wget -O- https://github.com/deluan/zsh-in-docker/releases/download/v1.2.1/zsh-in-docker.sh)"
 # Install fish

test/e2e/safe-chain-proxy.e2e.spec.js

@@ -0,0 +1,60 @@
+import { describe, it, before, beforeEach, afterEach } from "node:test";
+import { DockerTestContainer } from "./DockerTestContainer.js";
+import assert from "node:assert";
+
+describe("E2E: Safe chain proxy", () => {
+  let container;
+
+  before(async () => {
+    DockerTestContainer.buildImage();
+  });
+
+  beforeEach(async () => {
+    // Run a new Docker container for each test
+    container = new DockerTestContainer();
+    await container.start();
+
+    const installationShell = await container.openShell("zsh");
+    await installationShell.runCommand("safe-chain setup");
+  });
+
+  afterEach(async () => {
+    // Stop and clean up the container after each test
+    if (container) {
+      await container.stop();
+      container = null;
+    }
+  });
+
+  it(`safe-chain proxy respects upstream proxy settings`, async () => {
+    // Configure and start a proxy inside the container
+    const proxy = await container.openShell("zsh");
+    await proxy.runCommand(
+      `echo 'BasicAuth user password' >> /etc/tinyproxy/tinyproxy.conf`
+    );
+    await proxy.runCommand("tinyproxy");
+
+    const shell = await container.openShell("zsh");
+    await shell.runCommand(
+      'export HTTPS_PROXY="http://user:password@localhost:8888"'
+    );
+    const { output } = await shell.runCommand("npm install axios");
+
+    // Check if the installation was successful
+    assert(
+      output.includes("added") || output.includes("up to date"),
+      "npm install did not complete successfully"
+    );
+
+    const proxyLog = await container.openShell("zsh");
+    const { output: logOutput } = await proxyLog.runCommand(
+      "cat /var/log/tinyproxy/tinyproxy.log"
+    );
+
+    // Check if the proxy log contains entries for the npm install
+    assert(
+      logOutput.includes("CONNECT registry.npmjs.org:443"),
+      "Proxy log does not contain expected entries"
+    );
+  });
+});