modify do-nothing tests and add suite test

None of the tests of the form `assert foo == foo` were
deleted since perhaps the test should have been something
like

def unchanged(foo, f, a):
    return foo.func == f and foo.args == a
assert unchanged(Foo(x + 1), Foo, (x + 1,))

In at least one case the test was just affirming that the
expression no longer failed. (See test_issue_2983).