binary: improve tests for invalid numbers

[kytrinyx]

We should have separate tests for:

• alphabetic characters at the beginning of a valid binary number
• alphabetic characters at the end of a valid binary number
• alphabetic characters in the middle of an otherwise valid binary number
• invalid digits (e.g. 2)

If the test suite for binary has test cases that cover these edge cases, this issue can safely be closed.

See exercism/problem-specifications#95

[behrtam]

The current status looks like this ...

• alphabetic characters at the beginning of a valid binary number
• alphabetic characters at the end of a valid binary number
• alphabetic characters in the middle of an otherwise valid binary number
• invalid digits (e.g. 2)

So, we only need to add the case "10convert01" as suggested by @odeits.

Edit: Looks like we added those with #274 because of exercism/problem-specifications#95. So we need to clarify if we need all 3 test cases (binary numbers at start, end and both) and create a .json file in x-common.

[kytrinyx]

and create a .json file in x-common

Yeah, absolutely.

[arcuru]

Since binary is in the process of being deprecated (exercism/problem-specifications#279) this issue can probably be closed.

[kytrinyx]

Yeah, I think you're right about that.