Test Point Testing in C/C++

Introduction

Test Points provide an easy-to-use framework for solving a class of common yet difficult unit testing problems:

How can I observe and verify activity that occurs in another thread?

A couple of common scenarios that become a lot more testable via test points include:

• Verification of State machine operation
• Verification of asynchronous callbacks
• Verification of communication drivers

Instrumenting Source Code

Target threads are instrumented simply by placing lines of the following form into the source code:

...
/* a test point with no payload */
srTEST_POINT("first test point");

srTEST_POINT_DATA("second test point", myData, sizeofMyData);

srTEST_POINT_STR1("third test point", "payload with format string %d", myVar);

When this code is executed it broadcasts a message via the STRIDE runtime which is detected by the test (IM) thread if it is currently looking for test points (i.e. in a srTEST_POINT_WAIT()). We refer to this as a test point hit.

Instrumenting Test Code

The test code is instrumented using these steps:

1. Specify an expectation set (i.e. the test points that are expected to be hit)
2. Optionally, specify an unexpected set (i.e. the test points that are not expected to be hit)
3. Register the expectated and unexpected sets with the STRIDE runtime
4. If the activity we will be obvserving/verifying needs to be started (e.g. a state machine gets kicked off) this should be done after here
5. Wait for the expectation set to be satisfied or a timeout to occur

Here is an example:

#include <srtest.h>

void tf_testpoint_wait(void)
{
  /* specify expectation set */
  srTestPointExpect_t expected[]= {
        {"START"}, 
        {"ACTIVE"}, 
        {"IDLE"},
        {"END"}, 
        {0}};

  /* specify unexpectation set */
  srTestPointUnexpect_t unexpected[]= {
        {"INVALID"}, 
        {0}};

  /* register the expectation set with the STRIDE */
  srWORD handle;
  srTestPointExpect(expected, unexpected, srTEST_POINT_EXPECT_UNORDERED, &handle);

  /* start your asynchronous operation */
  ...

  /* wait for expectation set to be satisfied or a timeout to occur */
  srTEST_POINT_WAIT(handle, 1000);
}

#ifdef _SCL
#pragma scl_test_flist(“testfunc”, tf_testpoint_wait)
#endif

Reference

Test Point

To specify a test point you should use one of the following macros:

Test Point
srTEST_POINT(label)	label is a pointer to a null-terminated string
srTEST_POINT_DATA(label, data, size)	label is a pointer to a null-terminated string data is a pointer to a byte sequence size is the size of the data in bytes
srTEST_POINT_STR(label, message)	label is a pointer to a null-terminated string message is a pointer to a null-terminated string
srTEST_POINT_STR[1..4](label, message, ...)	label is a pointer to a null-terminated string message is a pointer to a null-terminated format string ... variable list (up to 4) matching the format string

Expectation Set

An expectation set is an array of srTestPointExpect_t structures. srTestPointExpect_t is typedef'd as follows:

typedef struct
{
    /* the label value is considered the test point's identity */
    const srCHAR *          label;
    /* optional, count specifies the number of times the test point is expected to be hit */ 
    srDWORD                 count;
    /* optional, predicate to use for payload validation against user data */ 
    srTestPointPredicate_t  predicate;
    /* optional, user data to validate the payload against */
    void *                  user;
} srTestPointExpect_t;

NOTES:

• The end of the array has to be marked by a srTestPointExpect_t set to all zero values
• The count, predicate and user members may be omitted in the array declaration (they will be automatically set to 0 by the compiler)
• A count value of either 0 or 1 is interpreted as 1
• The count could be set as "0 or more" by using the special srTEST_POINT_ANY_COUNT symbolic constant
• A predicate value 0 indicates that any associated with a test point payload will be ignored.
• A user value 0 indicates that there is no user data associated with this test point
• The label could be specified to everything else by using the special symbolic constant srTEST_POINT_EVERYTHING_ELSE. It is required to be the one end only (non zero) entry in the array.

srTestPointExpect

The srTestPointExpect() routine is used to register an expectation set.

srBOOL srTestPointExpect(srTestPointExpect_t* ptExpected, 
                         srTestPointExpectOrder_e eOrder, 
                         srTestPointExpectMembership_e eMembership, 
                         srWORD* pwHandle);

Parameters	Type	Description
ptExpected	Input	Pointer to an expectation set.
eOrder	Input	Expectation order. Possible values are: srTEST_POINT_EXPECT_ORDERED - the test points are expected to be hit exactly in the defined order srTEST_POINT_EXPECT_UNORDERED - the test points could to be hit in any order
eMembership	Input	Expectation membership. Possible values are: srTEST_POINT_EXPECT_EXCLUSIVE - any non expected test point hit will be treated as an error srTEST_POINT_EXPECT_NONEXCLUSIVE - non expected test points hit are ignored
pwHandle	Output	Handle that represents the registered expectation set

Return Value	Description
srBOOL	srTRUE on success, srFALSE otherwise.

srTestPointWait

The srTestPointWait() routine is used to wait for the expectation to be satisfied.

srBOOL srTestPointWait(srWORD wHandle, 
                       srTestCaseHandle_t tTestCase, 
                       srDWORD dwTimeout);

Parameters	Type	Description
wHandle	Input	Handle to a registered expectation set.
tTestCase	Input	Handle to a test case where the results would be reported. srTEST_CASE_DEFAULT can be used for the default test case.
dwTimeout	Input	Timeout value in milliseconds; 0 means just check without waiting.

Return Value	Description
srBOOL	srTRUE on success, srFALSE otherwise.

For convinience the following macros are provided:

#define srTEST_POINT_WAIT(handle, timeout) srTestPointWait(handle, srTEST_CASE_DEFAULT, timeout)
#define srTEST_POINT_CHECK(handle) srTestPointWait(handle, srTEST_CASE_DEFAULT, 0)

NOTES:

• The test thread blocks until either the expectation set is satisfied or the timeout elapses.
• All test points hit during the wait (both expected and unexpected) are added to the test report as testcase comments
• If an unexpected test point is encountered (either out of order or not in the expectation set), or the timeout period elapses before the expectation set is satisfied the current test immediately fails
• Once the wait is over (whether the expectation set has been satisfied or there has been a test failure), the current expectation set is automatically unregistered from the STRIDE runtime and the handle is released

Use Cases

0 or More Expectations

In some cases the expected test point pattern is something like:

• START
• PROGRESS

...

• END

where any number (0 or more) of PROGRESS are expected but doesn't matter how many.

To specify that use the special srTEST_POINT_ANY_COUNT constant:

#include <srtest.h>
 
void tf_testpoint_any(void)
{
  /* specify expectation set */
  srTestPointExpect_t expected[]= {
        {"START"}, 
        {"PROGRESS", srTEST_POINT_ANY_COUNT}, 
        {"END"}, 
        {0}};
...
}

Negative Expectations

Case 1. Need to run a scenario and verify that NONE of the test points are hit.

Dedicate a special test point, lets call it “NEGATIVE_FINAL”, and add it at the end of your test sequence then by setting the expectation “exclusively” to just that test point would allow testing that none of your other test points were hit:

#include <srtest.h>
 
void tf_testpoint_none(void)
{
  srTestPointExpect_t expected[]= {
        {"NEGATIVE_FINAL"}, 
        {0}};

  srWORD handle;
  srTestPointExpect(expected, srTEST_POINT_EXPECT_UNORDERED, srTEST_POINT_EXPECT_EXCLUSIVE, &handle);
...
}

Case 2. Need to verify that a subset of test points are not hit.

By expecting that all other (not in the negative subset) test points could be hit any number of times combined with the the technique described in case 1 would allow testing that a subset was to hit.

#include <srtest.h>
 
void tf_testpoint_none(void)
{
  srTestPointExpect_t expected[]= {
        {"TP_1", srTEST_POINT_ANY_COUNT}, 
        {"TP_2", srTEST_POINT_ANY_COUNT}, 
        ...
        {"TP_N", srTEST_POINT_ANY_COUNT}, 
        {"NEGATIVE_FINAL"}, 
        {0}};

  srWORD handle;
  srTestPointExpect(expected, srTEST_POINT_EXPECT_UNORDERED, srTEST_POINT_EXPECT_EXCLUSIVE, &handle);
...
}

Case 3. Want to return immediately from a test case if expectation fails.

Note that srTestPointWait() returns srFALSE if the expectation fails. By making the call an argument to srASSERT_TRUE(), you can automatically return from the current test case if the expectation is not met.

...

/* If expectation fails, returns immediately */
srASSERT_TRUE(srTestPointWait(handle, 1000));