Avoid seeding global random number generator in tests

[fxamacker]

Issue To Be Solved

Tests are seeding the global random number generator. However, seeding the global random number generator is not recommended since its global state can be changed by other packages at runtime.

Suggested Solution

Avoid using the global random number generator for tests, especially if randomized tests print out their nondeterministic seed to allow reproducing test failures.

Use rand.New to create, seed, and use non-global (private) random number generators. This will allow control over determinism vs non-determinism.