Refactor tests

[petrduda]

• [x] stop calling static methods in tests as non-static
• [x] use assertSame() where assertEquals() is not explicitly needed
• [x] use assertCount() after assertContains() for array comparison
• [x] add missing Assert::fail() in try+catch blocks when expecting exceptions
• [x] unify Assert::fail() message
• [x] replace Consistence\TestCase::ok() with expectNotToPerformAssertions()
• [x] use try+catch+fail when expecting exceptions with properties
• [x] rename data providers to singular where applicable
• [x] use DataProvider suffix for data providers
• [x] change data provider return type from array to Generator
• [x] declare data provider values on separate lines
• [x] isolate data provider cases using Closures
• [x] name data provider values
• [x] name data provider cases
• [x] extract multiple cases from test methods to data providers
• [x] remove unnecessary private methods for creating mocks