问题:

Whenever I try to run tests on Test Explorer from Visual Studio 2012, SOME test are being categorized as "External", even though the Group By is set as "Group By Project"

Then the source code is not recognized

回答1:

This is due the pdb file is not included in the compilation. If you're compiling in a solution configuration other than debug you must ensure that pdb is included.

To achieve that you must open the advanced build setting:

Right click on project and select properties
Click on build tab
Check that your configuration is selected in the "Configuration" dropdown
Click on advanced button.

In the new window you must select "pdb-only" in the debug info dropdown.

回答2:

This was happening for me but only when the combined length of the namespace, class, and test method exceeded 254 chars. (MS-Test, Visual Studio 2013 12.0.40629.00 Update 5)

namespace MyTests.HaveLong.Complicated.NamespaceAsWell.AsMuchAs.EightyFive.Chars.IfThatMatters
{
    [TestClass]
    public class A_Long_ClassName_MayAlso_Contribute_ToThe_Issue_ThisOneIs_EightyFive_Characters_Long
    {
        [TestMethod]
        public async Task This_IsAMsTest_TestMethod_WithAnEightyFive_CharacterName_WhichWillShow_UnderExternal()
        {
        }
        [TestMethod]
        public async Task This_IsAMsTest_TestMethod_WithAnEightyFour_CharacterName_WhichWontShowUnderExternal()
        {
        }
    }
}