Exercise: a table of cases

This time you write the tests, not the function. Fill in the cases table in cases_test.go: each case is a name name, an input x and the expected result want of abs. abs itself and the test that runs the table through t.Run are already in abs_test.go.

• {"negative", -7, 7} — the subtest TestAbs/negative
• {"zero", 0, 0}
• {"positive", 4, 4}

Constraints: the table has at least one negative x, a zero and at least one positive x; names are non-empty and distinct; every x appears in the table once and is from -1000 to 1000; want is the absolute value of x.

Do not add extra imports unless the task says so explicitly.