Add external calls validation

[piwonskp]

Fixes #904

[rjnrohit]

can you add a behaviour test where this check should throw an error?

warp/tests/behaviour/behaviour.test.ts

Lines 230 to 234 in 84b742a

	if (expectedResult === null) {
	expect(response.threw, `${name} - Function should throw`).to.be.true;
	error_message !== undefined &&
	response.error_message !== undefined &&
	expect(response.error_message).to.include(error_message);