Wrong CurrentCulture when running an nUnit test in TeamCity

You can force a specific culture for running your tests in your current thread System.Threading.Thread.CurrentThread

// set CurrentCulture to Invariant
Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
// set UI culture to invariant
Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;

You can also use CultureInfo.GetCultureInfo to provide the culture you want to use. This can be down in the SetUp part of your tests.

Remember to restore the culture to the previous one in your TearDown to ensure isolation

[TestFixture]
class MyTest {
  CultureInfo savedCulture;

  [SetUp]
  public void SetUp() {
    savedCulture = Thread.CurrentThread.CurrentCulture;
    Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
  }

  [TearDown]
  public void TearDown() {
    Thread.CurrentThread.CurrentCulture = savedCulture;
  }
}