chore: org check slug test suite (#3345)

* check slug test

* lint

packages/better-auth/src/plugins/organization/organization.test.ts

@@ -73,6 +73,26 @@ describe("organization", async (it) => {
 			organizationId,
 		);
 	});
+	it("should check if organization slug is available", async () => {
+		const { headers } = await signInWithTestUser();
+
+		const unusedSlug = await client.organization.checkSlug({
+			slug: "unused-slug",
+			fetchOptions: {
+				headers,
+			},
+		});
+		expect(unusedSlug.data?.status).toBe(true);
+
+		const existingSlug = await client.organization.checkSlug({
+			slug: "test",
+			fetchOptions: {
+				headers,
+			},
+		});
+		expect(existingSlug.error?.status).toBe(400);
+		expect(existingSlug.error?.message).toBe("slug is taken");
+	});
 
 	it("should create organization directly in the server without cookie", async () => {
 		const session = await client.getSession({