public void OnWritingSystemIDChange_DifferentId_OldIdIsRemoved()
{
var ws = new WritingSystemDefinition("fr");
RepositoryUnderTest.Set(ws);
Assert.IsTrue(RepositoryUnderTest.Contains("fr"));
ws.Language = "th";
RepositoryUnderTest.OnWritingSystemIDChange(ws, "fr");
Assert.IsFalse(RepositoryUnderTest.Contains("fr"));
Assert.IsTrue(RepositoryUnderTest.Contains("th"));
}