Report step number when a test case fails

Allow test code to declare a "step number". Report the current step
number when a test fails.
diff --git a/tests/suites/helpers.function b/tests/suites/helpers.function
index 1a524a6..d45fd4e 100644
--- a/tests/suites/helpers.function
+++ b/tests/suites/helpers.function
@@ -393,6 +393,7 @@
     const char *test;
     const char *filename;
     int line_no;
+    unsigned long step;
 }
 test_info;
 
@@ -423,6 +424,19 @@
 /*----------------------------------------------------------------------------*/
 /* Helper Functions */
 
+/** Set the test step number for failure reports.
+ *
+ * Call this function to display "step NNN" in addition to the line number
+ * and file name if a test fails. Typically the "step number" is the index
+ * of a for loop but it can be whatever you want.
+ *
+ * \param step  The step number to report.
+ */
+void test_set_step( unsigned long step )
+{
+    test_info.step = step;
+}
+
 void test_fail( const char *test, int line_no, const char* filename )
 {
     test_info.result = TEST_RESULT_FAILED;
diff --git a/tests/suites/host_test.function b/tests/suites/host_test.function
index 0f98d23..24d9b97 100644
--- a/tests/suites/host_test.function
+++ b/tests/suites/host_test.function
@@ -548,6 +548,7 @@
             {
                 test_info.result = TEST_RESULT_SUCCESS;
                 test_info.paramfail_test_state = PARAMFAIL_TESTSTATE_IDLE;
+                test_info.step = (unsigned long)( -1 );
 
 #if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
                 /* Suppress all output from the library unless we're verbose
@@ -624,9 +625,15 @@
                 {
                     total_errors++;
                     mbedtls_fprintf( stdout, "FAILED\n" );
-                    mbedtls_fprintf( stdout, "  %s\n  at line %d, %s\n",
-                                     test_info.test, test_info.line_no,
-                                     test_info.filename );
+                    mbedtls_fprintf( stdout, "  %s\n  at ",
+                                     test_info.test );
+                    if( test_info.step != (unsigned long)( -1 ) )
+                    {
+                        mbedtls_fprintf( stdout, "step %lu, ",
+                                         test_info.step );
+                    }
+                    mbedtls_fprintf( stdout, "line %d, %s",
+                                     test_info.line_no, test_info.filename );
                 }
                 fflush( stdout );
             }
diff --git a/tests/suites/target_test.function b/tests/suites/target_test.function
index 91f7198..937e8dd 100644
--- a/tests/suites/target_test.function
+++ b/tests/suites/target_test.function
@@ -375,6 +375,7 @@
     {
         ret = 0;
         test_info.result = TEST_RESULT_SUCCESS;
+        test_info.step = (unsigned long)( -1 );
         data_len = 0;
 
         data = receive_data( &data_len );