test: cover Linear env key logging (#30)

Co-authored-by: Sober <zerone0x@users.noreply.github.com>

Author: zerone0x

src/__tests__/config.test.ts

@@ -0,0 +1,49 @@
+import { getLinearApiToken } from '../utils/config.js';
+
+describe('getLinearApiToken', () => {
+  const originalArgv = process.argv;
+  const originalEnv = process.env;
+  let consoleErrorSpy: jest.SpyInstance;
+
+  beforeEach(() => {
+    process.argv = ['node', 'mcp-linear'];
+    process.env = { ...originalEnv };
+    delete process.env.LINEAR_API_TOKEN;
+    delete process.env.LINEAR_API_KEY;
+    delete process.env.LINEAR_WEBHOOK_SECRET;
+    delete process.env.MCP_LINEAR_DEBUG;
+    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    consoleErrorSpy.mockRestore();
+    process.argv = originalArgv;
+    process.env = originalEnv;
+  });
+
+  it('does not log LINEAR environment variable keys when debug logging is disabled', () => {
+    process.env.LINEAR_WEBHOOK_SECRET = 'present-but-not-a-token';
+
+    const token = getLinearApiToken();
+
+    expect(token).toBeUndefined();
+    expect(consoleErrorSpy).toHaveBeenCalledWith('API token not found in command line args or environment variables');
+    expect(consoleErrorSpy).not.toHaveBeenCalledWith(
+      'Environment variables:',
+      expect.arrayContaining(['LINEAR_WEBHOOK_SECRET']),
+    );
+  });
+
+  it('only logs LINEAR environment variable keys when explicit debug logging is enabled', () => {
+    process.env.LINEAR_WEBHOOK_SECRET = 'present-but-not-a-token';
+    process.env.MCP_LINEAR_DEBUG = 'true';
+
+    const token = getLinearApiToken();
+
+    expect(token).toBeUndefined();
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      'Environment variables:',
+      expect.arrayContaining(['LINEAR_WEBHOOK_SECRET']),
+    );
+  });
+});