uvm_test——测试用例的起点

在UVM平台验证中，所有的test cases都extends uvm_test,首先，来看源代码

//------------------------------------------------------------------------------
//
// CLASS: uvm_test
//
// This class is the virtual base class for the user-defined tests.
//
// The uvm_test virtual class should be used as the base class for user-defined
// tests. Doing so provides the ability to select which test to execute using
// the UVM_TESTNAME command line or argument to the <uvm_root::run_test> task.
//
// For example
//
//|  prompt> SIM_COMMAND +UVM_TESTNAME=test_bus_retry
//
// The global run_test() task should be specified inside an initial block
// such as
//
//|  initial run_test();
// 
// Multiple tests, identified by their type name, are compiled in and then
// selected for execution from the command line without need for recompilation.
// Random seed selection is also available on the command line.
//
// If +UVM_TESTNAME=test_name is specified, then an object of type 'test_name'
// is created by factory and phasing begins. Here, it is presumed that the
// test will instantiate the test environment, or the test environment will
// have already been instantiated before the call to run_test().
//
// If the specified test_name cannot be created by the <uvm_factory>, then a
// fatal error occurs. If run_test() is called without UVM_TESTNAME being
// specified, then all components constructed before the call to run_test will
// be cycled through their simulation phases.
//
// Deriving from uvm_test will allow you to distinguish tests from other
// component types that inherit from uvm_component directly. Such tests will
// automatically inherit features that may be added to uvm_test in the future.
//
//------------------------------------------------------------------------------

virtual class uvm_test extends uvm_component;
  
  // Function: new
  //
  // Creates and initializes an instance of this class using the normal
  // constructor arguments for <uvm_component>: ~name~ is the name of the
  // instance, and ~parent~ is the handle to the hierarchical parent, if any.

  function new (string name, uvm_component parent);
    super.new(name,parent);
  endfunction

  const static string type_name = "uvm_test";

  virtual function string get_type_name ();
    return type_name;
  endfunction

endclass

除了new() method之外，什么都没有。所有的test case 都扩展自uvm_test.一般的做法：

class default_test extends uvm_test

endclass

default_test 可以用来对验证平台做冒烟测试。

This class is the virtual base class for the user-defined tests.

User-defined test is derived from uvm_test, uvm_test is inherited from uvm_component.
Test defines the test scenario for the testbench.
test class contains the environment, configuration properties, class overrides etc.
A sequence/sequences are created and started in the test.

参考文献：

1 UVM Test . http://www.verificationguide.com/p/uvm-test.html