2.2 What does a DejaGnu test look like?

Each DejaGnu test is an expect script; the tests vary widely in complexity, depending on the nature of the tool and the feature tested.

Here is a very simple GDB test—one of the simplest tests shipped with DejaGnu (extracted from ‘gdb.t00/echo.exp’):(2)

# send a string to the GDB stdin:
send "echo Hello world!\n"

# inspect the GDB stdout for the correct reply,
# and determine whether the test passes or fails:
expect {
  -re "Hello world.*$prompt $"    { pass "Echo test" }
  -re "$prompt $"                 { fail "Echo test" }
  timeout                         { fail "(timeout) Echo test" }
  }

Though brief, this example is a complete test. It illustrates some of the main features of DejaGnu test scripts:

• The test case does not start the tested program (GDB in this case); all test scripts for interactive tools can assume the corresponding tool is running.
• Comments start with ‘#’.
• The main commands you use to control a tested program are send (to give it commands) and expect (to analyze its responses).
• The expect command uses a list of pairs; a pattern (regular expression if ‘-re’ specified), followed by an action to run if the pattern matches output from the program. Only the action for the first matching pattern will execute.
• Test cases use the commands pass and fail to record the test outcome.