Dealing with conditional verification logic using guard assertion

Question

I have parametrized test with 2 variants:

• NULL value

and

• any NOT NULL value

From this value is depends one assert:

• In case NULL it should be checked if object has field1 with value1
• In case NOT NULL it should be checked if object has field2 with value2

As I mentioned (see xUnit Tests Patterns ) using conditional statements in assert is anti-pattern.

How can I solve this problem properly?

I am trying at the moment to apply Guard assertion pattern:

• if-assertion is splitted into 2 assertions

• At the beginning there is test parameter check (NULL/NOT NULL) with guard assertion:

  it('case describing conditionalParamter=NOT NULL'):
   expect(conditionalParamter, 'to be a', 'string') // Guard assertion which can FAIL test. Is it OK? Can I simply **SKIP** assertion WITHOUT test failing 
   expect(myStub.args, 'to satisfy', [[ nonConditionalParamter, ExpressionWhichUsesNonNullConditionalParamterValue ]])
  it('case describing conditionalParamter= NULL')
   expect(conditionalParamter, 'to be falsy') // Guard assertion. The same issue
   expect(myStub.args, 'to satisfy', [[ nonConditionalParamter, ExpressionForNullConditionalParamterValue ]])
  

But in this case we have 2 failed assertions. Is it appropriate solution?

Is there better ways to solve problem?

• Ixrec: I have no idea how this particular unit testing framework works, but it sounds like you're saying it has a way of saying "use any non-null value for test 1 and null for test 2" and yet it does not have a way of saying "assert that this parameter was null (or not null)", which sounds massively broken to me. Is that the issue here?

Answer 1

Not sure what test framework you're using. But, this is what it might look like in RSpec (Ruby):

Method under test:

class Foo
 def bar(required_param, conditional_param = nil)
 return 'abc' if conditional_param.nil?
 '123'
 end
end

Tests:

describe Foo do
 subject(:foo) { described_class.new }
 describe '#bar' do
 subject(:bar) { foo.bar(required_param, conditional_param) }
 let(:required_param) { 'required_param' }
 context 'when conditional_param is nil (not present)' do
 let(:conditional_param) { nil }
 it 'returns abc' do
 expect(bar).to eq('abc')
 end
 end
 context 'when conditional_param is not nil' do
 let(:conditional_param) { true }
 it 'returns 123' do
 expect(bar).to eq('123')
 end
 end
 end
end