Potential bug in tests for testing headers and trailers

[parthea]

The check below fails because of 2 issues. Incorrect expected values, and incorrect boolean comparison

gapic-showcase/server/services/echo_service_test.go

Lines 125 to 127 in 961e217

	if expectHeadersAndTrailers && !reflect.DeepEqual([]string{"show", "case"}, m.trail) && !reflect.DeepEqual([]string{"showcaseHeader, anotherHeader"}, m.head) {
	m.t.Errorf("Unary stream did not get all expected headers and trailers.\nGot these headers: %+v\nGot these trailers: %+v", m.head, m.trail)
	}

1. In the code below, the expected values appear to be incorrect. We have "showcaseHeader, anotherHeader" instead of "showcaseHeader", "anotherHeader"

 !reflect.DeepEqual([]string{"showcaseHeader, anotherHeader"}

2. We have && in the boolean check for verifying the value of both headers and trailers. It should be || so that if either check for headers or trailers fails, we get an error condition.

The way it is written now
NOT <condition> && NOT <condition> -> both conditions must be false for the error condition to appear

The way it should be
NOT <condition> || NOT <condition> -> only one condition should be false for the error condition to appear