1, variable context has two level, testset and testcase;
2, testset level variables can be used in whole test suite, while testcase level variables can only be used in testcase;
3, when variable binds with functions, the funtions will be called and the result will be set to the variable.
1, testset and testcase are in different context level;
2, testset context will be initialized when a file is loaded, and testcase level context initializes when each testcase starts;
3, testcase context should inherit from testset context configs, and the testcase context has high priority.