diff --git a/apps/web/src/lib/api/admin.test.ts b/apps/web/src/lib/api/admin.test.ts
new file mode 100644
index 0000000..3f16ad9
--- /dev/null
+++ b/apps/web/src/lib/api/admin.test.ts
@@ -0,0 +1,60 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import * as client from "./client";
+import { fetchAdminUsers, inviteUser, updateUser, deactivateUser } from "./admin";
+
+vi.mock("./client");
+
+beforeEach((): void => {
+  vi.clearAllMocks();
+});
+
+describe("fetchAdminUsers", (): void => {
+  it("calls admin/users endpoint without params when none provided", async (): Promise<void> => {
+    vi.mocked(client.apiGet).mockResolvedValueOnce({ data: [], meta: {} } as never);
+    await fetchAdminUsers();
+    expect(client.apiGet).toHaveBeenCalledWith("/api/admin/users");
+  });
+
+  it("appends page and limit params when provided", async (): Promise<void> => {
+    vi.mocked(client.apiGet).mockResolvedValueOnce({ data: [], meta: {} } as never);
+    await fetchAdminUsers(2, 50);
+    expect(client.apiGet).toHaveBeenCalledWith("/api/admin/users?page=2&limit=50");
+  });
+
+  it("throws on API error", async (): Promise<void> => {
+    vi.mocked(client.apiGet).mockRejectedValueOnce(new Error("Network error"));
+    await expect(fetchAdminUsers()).rejects.toThrow("Network error");
+  });
+});
+
+describe("inviteUser", (): void => {
+  it("posts to invite endpoint", async (): Promise<void> => {
+    vi.mocked(client.apiPost).mockResolvedValueOnce({ id: "inv-1" } as never);
+    await inviteUser({
+      email: "a@b.com",
+      name: "Alice",
+      workspaceId: "ws-1",
+      role: "MEMBER" as never,
+    });
+    expect(client.apiPost).toHaveBeenCalledWith(
+      "/api/admin/users/invite",
+      expect.objectContaining({ email: "a@b.com" })
+    );
+  });
+});
+
+describe("updateUser", (): void => {
+  it("patches correct endpoint with dto", async (): Promise<void> => {
+    vi.mocked(client.apiPatch).mockResolvedValueOnce({ id: "u1", name: "Bob" } as never);
+    await updateUser("u1", { name: "Bob" });
+    expect(client.apiPatch).toHaveBeenCalledWith("/api/admin/users/u1", { name: "Bob" });
+  });
+});
+
+describe("deactivateUser", (): void => {
+  it("deletes correct endpoint", async (): Promise<void> => {
+    vi.mocked(client.apiDelete).mockResolvedValueOnce({} as never);
+    await deactivateUser("u1");
+    expect(client.apiDelete).toHaveBeenCalledWith("/api/admin/users/u1");
+  });
+});
diff --git a/apps/web/src/lib/api/teams.test.ts b/apps/web/src/lib/api/teams.test.ts
new file mode 100644
index 0000000..dff229a
--- /dev/null
+++ b/apps/web/src/lib/api/teams.test.ts
@@ -0,0 +1,53 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import * as client from "./client";
+import { fetchTeams, createTeam, fetchTeamMembers } from "./teams";
+
+vi.mock("./client");
+
+const localStorageMock = {
+  getItem: vi.fn().mockReturnValue("ws-1"),
+  setItem: vi.fn(),
+  clear: vi.fn(),
+  removeItem: vi.fn(),
+  length: 0,
+  key: vi.fn(),
+};
+Object.defineProperty(window, "localStorage", { value: localStorageMock });
+
+beforeEach((): void => {
+  vi.clearAllMocks();
+  localStorageMock.getItem.mockReturnValue("ws-1");
+});
+
+describe("fetchTeams", (): void => {
+  it("calls teams endpoint for active workspace", async (): Promise<void> => {
+    vi.mocked(client.apiGet).mockResolvedValueOnce([] as never);
+    await fetchTeams();
+    expect(client.apiGet).toHaveBeenCalledWith("/api/workspaces/ws-1/teams", "ws-1");
+  });
+
+  it("throws if no workspace id in localStorage", async (): Promise<void> => {
+    localStorageMock.getItem.mockReturnValue(null);
+    await expect(fetchTeams()).rejects.toThrow();
+  });
+});
+
+describe("createTeam", (): void => {
+  it("posts to teams endpoint", async (): Promise<void> => {
+    vi.mocked(client.apiPost).mockResolvedValueOnce({ id: "t1", name: "Dev" } as never);
+    await createTeam({ name: "Dev" });
+    expect(client.apiPost).toHaveBeenCalledWith(
+      "/api/workspaces/ws-1/teams",
+      expect.objectContaining({ name: "Dev" }),
+      "ws-1"
+    );
+  });
+});
+
+describe("fetchTeamMembers", (): void => {
+  it("calls members endpoint for team", async (): Promise<void> => {
+    vi.mocked(client.apiGet).mockResolvedValueOnce([] as never);
+    await fetchTeamMembers("t-1");
+    expect(client.apiGet).toHaveBeenCalledWith("/api/workspaces/ws-1/teams/t-1/members", "ws-1");
+  });
+});
diff --git a/apps/web/src/lib/api/workspaces.test.ts b/apps/web/src/lib/api/workspaces.test.ts
new file mode 100644
index 0000000..5cae481
--- /dev/null
+++ b/apps/web/src/lib/api/workspaces.test.ts
@@ -0,0 +1,65 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import * as client from "./client";
+import {
+  fetchUserWorkspaces,
+  fetchWorkspaceMembers,
+  addWorkspaceMember,
+  updateWorkspaceMemberRole,
+  removeWorkspaceMember,
+} from "./workspaces";
+
+vi.mock("./client");
+
+beforeEach((): void => {
+  vi.clearAllMocks();
+});
+
+describe("fetchUserWorkspaces", (): void => {
+  it("calls correct endpoint", async (): Promise<void> => {
+    vi.mocked(client.apiGet).mockResolvedValueOnce([] as never);
+    await fetchUserWorkspaces();
+    expect(client.apiGet).toHaveBeenCalledWith("/api/workspaces");
+  });
+});
+
+describe("fetchWorkspaceMembers", (): void => {
+  it("calls correct endpoint with workspace id", async (): Promise<void> => {
+    vi.mocked(client.apiGet).mockResolvedValueOnce([] as never);
+    await fetchWorkspaceMembers("ws-1");
+    expect(client.apiGet).toHaveBeenCalledWith("/api/workspaces/ws-1/members");
+  });
+
+  it("throws on error", async (): Promise<void> => {
+    vi.mocked(client.apiGet).mockRejectedValueOnce(new Error("Forbidden"));
+    await expect(fetchWorkspaceMembers("ws-1")).rejects.toThrow("Forbidden");
+  });
+});
+
+describe("addWorkspaceMember", (): void => {
+  it("posts to correct endpoint", async (): Promise<void> => {
+    vi.mocked(client.apiPost).mockResolvedValueOnce({} as never);
+    await addWorkspaceMember("ws-1", { userId: "u1", role: "MEMBER" as never });
+    expect(client.apiPost).toHaveBeenCalledWith("/api/workspaces/ws-1/members", {
+      userId: "u1",
+      role: "MEMBER",
+    });
+  });
+});
+
+describe("updateWorkspaceMemberRole", (): void => {
+  it("patches correct endpoint", async (): Promise<void> => {
+    vi.mocked(client.apiPatch).mockResolvedValueOnce({} as never);
+    await updateWorkspaceMemberRole("ws-1", "u1", { role: "ADMIN" as never });
+    expect(client.apiPatch).toHaveBeenCalledWith("/api/workspaces/ws-1/members/u1", {
+      role: "ADMIN",
+    });
+  });
+});
+
+describe("removeWorkspaceMember", (): void => {
+  it("calls delete on correct endpoint", async (): Promise<void> => {
+    vi.mocked(client.apiDelete).mockResolvedValueOnce(undefined as never);
+    await removeWorkspaceMember("ws-1", "u1");
+    expect(client.apiDelete).toHaveBeenCalledWith("/api/workspaces/ws-1/members/u1");
+  });
+});