Output and Exceptions

• Sometimes you want to test I/O
• Start with the basic outline from before

  • #define BOOST_TEST_MODULE  f_to_c_test_suite
    #include <boost/test/unit_test.hpp>
    #include <boost/test/included/unit_test.hpp>
    
    // new to catch output
    #include <boost/test/tools/output_test_stream.hpp>
    
    #include "FtoC.h"
    
    // so we can use the elements of the output_test_stream without
    // a horrid list of namespaces
    using boost::test_tools::output_test_stream;
    using namespace std; 

• Testing output
  • reference
  • You can capture output intended for the standard output.
  • This is some c++ stream magic

  • 
    output_test_stream output;
    streambuf * old = cout.rdbuf(output.rdbuf());
    // force the error
    
    FtoC(-500);
    
    // restore cout.
    cout.rdbuf(old);
              

  • After this runs, output contains the value of anything written to cout.
  • There five member functions to an output_test_stream
    • is_empty(bool flush)
    • check_length(size_t len, bool flush)
    • is_equal(string s, bool flush)
    • match_pattern(bool flush)
    • flush()
  • In each case, the flush flag indicates to clear the stream.
  • We will not discuss match_pattern

  • BOOST_AUTO_TEST_CASE(Front_Error_Test) {
        output_test_stream output;
        streambuf * old = cout.rdbuf(output.rdbuf());
    
        string goodMessage = "Illegal Temperature in F.\n";
        string goodMessage = "illegal temp\n";
    
        FtoC(-500);
    
        cout.rdbuf(old);
    
        BOOST_TEST(not output.is_empty(false));
    
        BOOST_TEST(output.check_length(goodMessage.size(),false));
        BOOST_TEST(output.check_length(badMessage.size(),false), "Expect fail");
        BOOST_TEST(output.is_equal(goodMessage,false));
        BOOST_TEST(output.is_equal(badMessage,false),"Expect Fail");
    
        // clean the output stream for reuse.
        // not needed here, but ...
        output.flush();
    
        return;
    } 

• Exceptions
  • reference
  • BOOST_REQUIRE_TROW(call, exception_type)
  • BOOST_CHECK_TROW(call, exception_type)
  • BOOST_WARN_TROW(call, exception_type)
    • See this reference for warning levels.
  • These check for exceptions
    • You expect call to throw an exception of exception_type
    • Reports error if not exception is thrown
    • Aborts the test routine if the wrong exception is thrown.
      • It does this via an exception so it can be caught.
  • So We can use these in a test

    •     // these will warn if the exception does not occur
          BOOST_CHECK_THROW(CtoF(-400),exception);
          BOOST_CHECK_THROW(CtoF(-400),invalid_argument);
      
          // we expect an exception, but one does not occur
          cout << "Here is an error" << endl;
          BOOST_CHECK_THROW(CtoF(400),exception);
          cout << "After error " << endl;
          cout << endl;
      
          // these will bomb if the exception does not occur.
          BOOST_REQUIRE_THROW(CtoF(-400),exception);
          BOOST_REQUIRE_THROW(CtoF(-400),invalid_argument);
      
          // require a throw but it does not happen.
          cout << "Here is an error, we required a throw but it did not" << endl;
          BOOST_REQUIRE_THROW(CtoF(400),invalid_argument);
          cout << "Did not get here." << endl; 

  • The library will catch throws you don't but it will kill that test.
    • This routine will be killed.
    • But the tests will continue.
    • < pre class="prettyprint"> BOOST_AUTO_TEST_CASE(uncaught_exception_test) { // this will throw an exception and abort the test. cout << "About to throw an error " << end; CtoF(-400); cout << "Boy is that cold" << endl; }
  • BOOST_*_NO_THROW(call)
    • Opposite of above.

    • BOOST_AUTO_TEST_CASE(no_throw_test) {
          cout << "We made it to the no_throw case." << endl;
          BOOST_CHECK_NO_THROW(CtoF(100));
          cout << "This should complain " << endl;
          BOOST_CHECK_NO_THROW(CtoF(-2100));
          cout << "Done with the no_throw case." <<endl;
      } 

• See FtoCTest4.cpp