PowerShell is case insensitive by default.

Currently any solution that removes the "_" and "-" will pass all tests because the case of the resulting string doest matter.

The "Should -Be" is case insensitve per the Pester docs: https://pester.dev/docs/v4/usage/assertions#beexactly
To solve this "Should -BeExactly" should be used.

Compare-Object is case insensitive unless the "-CaseSensitive" flag is provided: https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/compare-object?view=powershell-7.3
To solve this issue the "-CaseSensitive" parameter should be specified.

It appears C# is still broken:

I just failed a random test where the input was [9, 9, 33]. It says the expected output is 0. However, there is an example in the problem explination where the input is [2, 2, 2] and the output is 2.

In the example of [9, 9, 33] the output should be 9 (the value of the start number).

I agree. I just failed a random test where the input was [9, 9, 33]. It says the expected output is 0. However, there is an example in the problem explination where the input is [2, 2, 2] and the output is 2.

In the example of [9, 9, 33] the output should be 9 (the value of the start number).