diff --git a/tests/oauth-client-info.test.ts b/tests/oauth-client-info.test.ts
new file mode 100644
index 00000000..a2ea8d82
--- /dev/null
+++ b/tests/oauth-client-info.test.ts
@@ -0,0 +1,112 @@
+import { afterEach, describe, expect, it } from 'vitest';
+import type { ServerDefinition } from '../src/config.js';
+import { buildStaticClientInformation, resolveOAuthClientSecret } from '../src/oauth-client-info.js';
+
+const SECRET_ENV = 'MCPORTER_TEST_CLIENT_INFO_SECRET';
+
+function definition(overrides: Partial<ServerDefinition> = {}): ServerDefinition {
+  return {
+    name: 'test-server',
+    command: { kind: 'http', url: new URL('https://example.com/mcp') },
+    auth: 'oauth',
+    ...overrides,
+  };
+}
+
+afterEach(() => {
+  delete process.env[SECRET_ENV];
+});
+
+describe('resolveOAuthClientSecret', () => {
+  it('returns the referenced env var value', () => {
+    process.env[SECRET_ENV] = 'from-env';
+    expect(resolveOAuthClientSecret(definition({ oauthClientSecretEnv: SECRET_ENV }))).toBe('from-env');
+  });
+
+  it('throws when the referenced env var is unset', () => {
+    expect(() => resolveOAuthClientSecret(definition({ oauthClientSecretEnv: SECRET_ENV }))).toThrow(SECRET_ENV);
+  });
+
+  it('throws on an empty-string env value regardless of rejectBlank', () => {
+    process.env[SECRET_ENV] = '';
+    expect(() => resolveOAuthClientSecret(definition({ oauthClientSecretEnv: SECRET_ENV }))).toThrow(SECRET_ENV);
+  });
+
+  it('returns a whitespace-only env value when rejectBlank is not set', () => {
+    process.env[SECRET_ENV] = '   ';
+    expect(resolveOAuthClientSecret(definition({ oauthClientSecretEnv: SECRET_ENV }))).toBe('   ');
+  });
+
+  it('throws on a whitespace-only env value when rejectBlank is set', () => {
+    process.env[SECRET_ENV] = '   ';
+    expect(() =>
+      resolveOAuthClientSecret(definition({ oauthClientSecretEnv: SECRET_ENV }), { rejectBlank: true })
+    ).toThrow(SECRET_ENV);
+  });
+
+  it('returns the inline secret when no env var is configured', () => {
+    expect(resolveOAuthClientSecret(definition({ oauthClientSecret: 'inline' }))).toBe('inline');
+  });
+
+  it('returns undefined when neither env var nor inline secret is set', () => {
+    expect(resolveOAuthClientSecret(definition())).toBeUndefined();
+  });
+});
+
+describe('buildStaticClientInformation', () => {
+  it('returns undefined when no client id is configured', () => {
+    expect(buildStaticClientInformation(definition())).toBeUndefined();
+  });
+
+  it('emits the fixed grant and response types for a static client', () => {
+    expect(buildStaticClientInformation(definition({ oauthClientId: 'client-1' }))).toMatchObject({
+      client_id: 'client-1',
+      grant_types: ['authorization_code', 'refresh_token'],
+      response_types: ['code'],
+    });
+  });
+
+  it('includes the resolved client secret', () => {
+    process.env[SECRET_ENV] = 'from-env';
+    const info = buildStaticClientInformation(
+      definition({ oauthClientId: 'client-1', oauthClientSecretEnv: SECRET_ENV })
+    );
+    expect(info).toMatchObject({ client_secret: 'from-env' });
+  });
+
+  it('omits the client secret when none is configured', () => {
+    const info = buildStaticClientInformation(definition({ oauthClientId: 'client-1' }));
+    expect(info).not.toHaveProperty('client_secret');
+  });
+
+  it('propagates the required-secret error when the configured env var is unset', () => {
+    expect(() =>
+      buildStaticClientInformation(definition({ oauthClientId: 'client-1', oauthClientSecretEnv: SECRET_ENV }))
+    ).toThrow(SECRET_ENV);
+  });
+
+  it('includes redirect_uris derived from a URL redirect', () => {
+    const info = buildStaticClientInformation(definition({ oauthClientId: 'client-1' }), {
+      redirectUrl: new URL('http://127.0.0.1:8080/callback'),
+    });
+    expect(info).toMatchObject({ redirect_uris: ['http://127.0.0.1:8080/callback'] });
+  });
+
+  it('accepts a string redirect and omits redirect_uris when none is given', () => {
+    const withRedirect = buildStaticClientInformation(definition({ oauthClientId: 'client-1' }), {
+      redirectUrl: 'http://127.0.0.1:9090/cb',
+    });
+    expect(withRedirect).toMatchObject({ redirect_uris: ['http://127.0.0.1:9090/cb'] });
+    expect(buildStaticClientInformation(definition({ oauthClientId: 'client-1' }))).not.toHaveProperty('redirect_uris');
+  });
+
+  it('includes token_endpoint_auth_method only when configured', () => {
+    const withMethod = buildStaticClientInformation(
+      definition({ oauthClientId: 'client-1', oauthTokenEndpointAuthMethod: 'client_secret_post' })
+    );
+    expect(withMethod).toMatchObject({ token_endpoint_auth_method: 'client_secret_post' });
+    expect(buildStaticClientInformation(definition({ oauthClientId: 'client-1' }))).not.toHaveProperty(
+      'token_endpoint_auth_method'
+    );
+  });
+});