diff --git a/src/commands/use.spec.ts b/src/commands/use.spec.ts
new file mode 100644
index 00000000000..880cd0796ac
--- /dev/null
+++ b/src/commands/use.spec.ts
@@ -0,0 +1,128 @@
+import { expect } from "chai";
+import * as sinon from "sinon";
+import { RC } from "../rc";
+
+import { command } from "./use";
+import * as projects from "../management/projects";
+import * as studio from "../management/studio";
+import * as prompt from "../prompt";
+import * as utils from "../utils";
+import * as auth from "../requireAuth";
+import * as detect from "../detectProjectRoot";
+import * as rcModule from "../rc";
+import { FirebaseProjectMetadata } from "../types/project";
+
+describe("use command", () => {
+  let getProjectStub: sinon.SinonStub;
+  let makeActiveProjectStub: sinon.SinonStub;
+  let detectProjectRootStub: sinon.SinonStub;
+
+  beforeEach(() => {
+    getProjectStub = sinon.stub(projects, "getProject").resolves({
+      projectId: "my-project",
+      projectNumber: "123",
+      lifecycleState: "ACTIVE",
+      name: "projects/my-project",
+      createTime: "2026-04-23T00:00:00Z",
+      parent: { type: "organization", id: "123" },
+    } as projects.ProjectInfo);
+    sinon.stub(projects, "listFirebaseProjects").resolves([
+      {
+        name: "projects/my-project",
+        projectId: "my-project",
+        projectNumber: "123",
+      },
+    ] as FirebaseProjectMetadata[]);
+    sinon.stub(studio, "updateStudioFirebaseProject").resolves();
+    makeActiveProjectStub = sinon.stub(utils, "makeActiveProject").returns();
+    sinon.stub(prompt, "select").resolves("my-project");
+    sinon.stub(prompt, "input").resolves("staging");
+    sinon.stub(auth, "requireAuth").resolves();
+    detectProjectRootStub = sinon.stub(detect, "detectProjectRoot").returns("/path/to/project");
+    sinon
+      .stub(rcModule, "loadRC")
+      .callsFake((options: { [other: string]: any; cwd?: string }) => options.rc || new RC());
+  });
+
+  afterEach(() => {
+    sinon.restore();
+  });
+
+  it("should throw if not in a project root", async () => {
+    detectProjectRootStub.returns(undefined);
+    const options = { rc: new RC() };
+    await expect(command.runner()("my-project", options)).to.be.rejectedWith(
+      /must be run from a Firebase project directory/,
+    );
+  });
+
+  it("should set active project for existing alias", async () => {
+    const rc = new RC(undefined, { projects: { staging: "my-project" } });
+    const options = { rc, projectRoot: "/path/to/project" };
+
+    await command.runner()("staging", options);
+
+    expect(makeActiveProjectStub).to.have.been.calledWith("/path/to/project", "staging");
+  });
+
+  it("should set active project for project ID directly", async () => {
+    const rc = new RC();
+    const options = { rc, projectRoot: "/path/to/project" };
+
+    await command.runner()("my-project", options);
+
+    expect(makeActiveProjectStub).to.have.been.calledWith("/path/to/project", "my-project");
+  });
+
+  it("should throw if alias not found and not valid project ID", async () => {
+    const rc = new RC();
+    const options = { rc, projectRoot: "/path/to/project" };
+    getProjectStub.rejects(new Error("Not found"));
+
+    await expect(command.runner()("nonexistent", options)).to.be.rejectedWith(
+      /Invalid project selection/,
+    );
+  });
+
+  it("should unalias a project", async () => {
+    const rc = new RC(undefined, { projects: { staging: "my-project" } });
+    const options = { rc, projectRoot: "/path/to/project", unalias: "staging" };
+
+    await command.runner()(undefined, options);
+
+    expect(rc.hasProjectAlias("staging")).to.be.false;
+  });
+
+  it("should add a new alias interactively", async () => {
+    const rc = new RC();
+    const options = { rc, projectRoot: "/path/to/project", add: true, interactive: true };
+
+    await command.runner()(undefined, options);
+
+    expect(rc.resolveAlias("staging")).to.equal("my-project");
+    expect(makeActiveProjectStub).to.have.been.calledWith("/path/to/project", "staging");
+  });
+
+  it("should clear the active project", async () => {
+    const rc = new RC();
+    const options = { rc, projectRoot: "/path/to/project", clear: true, projectAlias: "staging" };
+
+    await command.runner()(undefined, options);
+
+    expect(makeActiveProjectStub).to.have.been.calledWith("/path/to/project", undefined);
+  });
+
+  it("should display generic use info if no arguments passed", async () => {
+    const rc = new RC(undefined, { projects: { staging: "my-project" } });
+    const options = {
+      rc,
+      projectRoot: "/path/to/project",
+      projectAlias: "staging",
+      project: "my-project",
+    };
+
+    const result = await command.runner()(undefined, options);
+
+    expect(result).to.equal("my-project");
+  });
+});