feat: finish the docker plugin (B15)

plugins/docker/tests/backend/fake-ssh.ts

@@ -0,0 +1,84 @@
+import { EventEmitter } from "node:events";
+
+/** An ssh2 exec channel: stdout on "data", stderr on `stderr`, then "close". */
+export class FakeStream extends EventEmitter {
+  stderr = new EventEmitter();
+  written: string[] = [];
+  ended = false;
+  window: [number, number] | null = null;
+
+  write(data: string) {
+    this.written.push(data);
+    return true;
+  }
+
+  end() {
+    this.ended = true;
+  }
+
+  setWindow(rows: number, cols: number) {
+    this.window = [rows, cols];
+  }
+
+  /** Emits output and exits, on the next tick like a real channel. */
+  finish(stdout: string, code = 0, stderr = "") {
+    setImmediate(() => {
+      if (stdout) this.emit("data", Buffer.from(stdout));
+      if (stderr) this.stderr.emit("data", Buffer.from(stderr));
+      this.emit("close", code);
+    });
+  }
+}
+
+export type ExecReply =
+  | { stdout?: string; stderr?: string; code?: number }
+  | ((stream: FakeStream) => void);
+
+/**
+ * An ssh2 Client that answers exec by the first matching pattern. A reply
+ * may be a function for a long-lived channel such as a console.
+ */
+export class FakeClient extends EventEmitter {
+  commands: string[] = [];
+  streams: FakeStream[] = [];
+  ended = false;
+
+  constructor(private replies: Array<[RegExp, ExecReply]> = []) {
+    super();
+  }
+
+  reply(pattern: RegExp, reply: ExecReply) {
+    this.replies.unshift([pattern, reply]);
+  }
+
+  exec(
+    command: string,
+    optionsOrCallback: unknown,
+    maybeCallback?: (err: Error | undefined, stream: FakeStream) => void,
+  ) {
+    const callback = (
+      typeof optionsOrCallback === "function"
+        ? optionsOrCallback
+        : maybeCallback
+    ) as (err: Error | undefined, stream: FakeStream) => void;
+    this.commands.push(command);
+    const stream = new FakeStream();
+    this.streams.push(stream);
+    const match = this.replies.find(([pattern]) => pattern.test(command));
+    callback(undefined, stream);
+    if (!match) {
+      stream.finish("");
+      return this;
+    }
+    const reply = match[1];
+    if (typeof reply === "function") reply(stream);
+    else stream.finish(reply.stdout ?? "", reply.code ?? 0, reply.stderr ?? "");
+    return this;
+  }
+
+  end() {
+    if (this.ended) return;
+    this.ended = true;
+    this.emit("close");
+  }
+}