1 Writing TAP Tests 2 3Introduction 4 5 This is a guide for users of the C TAP Harness package or similar 6 TAP-based test harnesses explaining how to write tests. If your 7 package uses C TAP Harness as the test suite driver, you may want to 8 copy this document to an appropriate file name in your test suite as 9 documentation for contributors. 10 11About TAP 12 13 TAP is the Test Anything Protocol, a protocol for communication 14 between test cases and a test harness. This is the protocol used by 15 Perl for its internal test suite and for nearly all Perl modules, 16 since it's the format used by the build tools for Perl modules to run 17 tests and report their results. 18 19 A TAP-based test suite works with a somewhat different set of 20 assumptions than an xUnit test suite. In TAP, each test case is a 21 separate program. That program, when run, must produce output in the 22 following format: 23 24 1..4 25 ok 1 - the first test 26 ok 2 27 # a diagnostic, ignored by the harness 28 not ok 3 - a failing test 29 ok 4 # skip a skipped test 30 31 The output should all go to standard output. The first line specifies 32 the number of tests to be run, and then each test produces output that 33 looks like either "ok <n>" or "not ok <n>" depending on whether the 34 test succeeded or failed. Additional information about the test can 35 be provided after the "ok <n>" or "not ok <n>", but is optional. 36 Additional diagnostics and information can be provided in lines 37 beginning with a "#". 38 39 Processing directives are supported after the "ok <n>" or "not ok <n>" 40 and start with a "#". The main one of interest is "# skip" which says 41 that the test was skipped rather than successful and optionally gives 42 the reason. Also supported is "# todo", which normally annotates a 43 failing test and indicates that test is expected to fail, optionally 44 providing a reason for why. 45 46 There are three more special cases. First, the initial line stating 47 the number of tests to run, called the plan, may appear at the end of 48 the output instead of the beginning. This can be useful if the number 49 of tests to run is not known in advance. Second, a plan in the form: 50 51 1..0 # skip entire test case skipped 52 53 can be given instead, which indicates that this entire test case has 54 been skipped (generally because it depends on facilities or optional 55 configuration which is not present). Finally, if the test case 56 encounters a fatal error, it should print the text: 57 58 Bail out! 59 60 on standard output, optionally followed by an error message, and then 61 exit. This tells the harness that the test aborted unexpectedly. 62 63 The exit status of a successful test case should always be 0. The 64 harness will report the test as "dubious" if all the tests appeared to 65 succeed but it exited with a non-zero status. 66 67Writing TAP Tests 68 69 Environment 70 71 One of the special features of C TAP Harness is the environment that 72 it sets up for your test cases. If your test program is called under 73 the runtests driver, the environment variables SOURCE and BUILD will 74 be set to the top of the test directory in the source tree and the top 75 of the build tree, respectively. You can use those environment 76 variables to locate additional test data, programs and libraries built 77 as part of your software build, and other supporting information 78 needed by tests. 79 80 The C and shell TAP libraries support a test_file_path() function, 81 which looks for a file under the build tree and then under the source 82 tree, using the BUILD and SOURCE environment variables, and return the 83 full path to the file. This can be used to locate supporting data 84 files. 85 86 Perl 87 88 Since TAP is the native test framework for Perl, writing TAP tests in 89 Perl is very easy and extremely well-supported. If you've never 90 written tests in Perl before, start by reading the documentation for 91 Test::Tutorial and Test::Simple, which walks you through the basics, 92 including the TAP output syntax. Then, the best Perl module to use 93 for serious testing is Test::More, which provides a lot of additional 94 functions over Test::Simple including support for skipping tests, 95 bailing out, and not planning tests in advance. See the documentation 96 of Test::More for all the details and lots of examples. 97 98 C TAP Harness can run Perl test scripts directly and interpret the 99 results correctly, and similarly the Perl Test::Harness module and 100 prove command can run TAP tests written in other languages using, for 101 example, the TAP library that comes with C TAP Harness. You can, if 102 you wish, use the library that comes with C TAP Harness but use prove 103 instead of runtests for running the test suite. 104 105 C 106 107 C TAP Harness provides a basic TAP library that takes away most of the 108 pain of writing TAP test cases in C. A C test case should start with 109 a call to plan(), passing in the number of tests to run. Then, each 110 test should use is_int(), is_string(), is_double(), or is_hex() as 111 appropriate to compare expected and seen values, or ok() to do a 112 simpler boolean test. The is_*() functions take expected and seen 113 values and then a printf-style format string explaining the test 114 (which may be NULL). ok() takes a boolean and then the printf-style 115 string. 116 117 Here's a complete example test program that uses the C TAP library: 118 119 #include <stddef.h> 120 #include <tap/basic.h> 121 122 int 123 main(void) 124 { 125 plan(4); 126 127 ok(1, "the first test"); 128 is_int(42, 42, NULL); 129 diag("a diagnostic, ignored by the harness"); 130 ok(0, "a failing test"); 131 skip("a skipped test"); 132 133 return 0; 134 } 135 136 This test program produces the output shown above in the section on 137 TAP and demonstrates most of the functions. The other functions of 138 interest are sysdiag() (like diag() but adds strerror() results), 139 bail() and sysbail() for fatal errors, skip_block() to skip a whole 140 block of tests, and skip_all() which is called instead of plan() to 141 skip an entire test case. 142 143 The C TAP library also provides plan_lazy(), which can be called 144 instead of plan(). If plan_lazy() is called, the library will keep 145 track of how many test results are reported and will print out the 146 plan at the end of execution of the program. This should normally be 147 avoided since the test may appear to be successful even if it exits 148 prematurely, but it can make writing tests easier in some 149 circumstances. 150 151 Complete API documentation for the basic C TAP library that comes with 152 C TAP Harness is available at: 153 154 <http://www.eyrie.org/~eagle/software/c-tap-harness/> 155 156 It's common to need additional test functions and utility functions 157 for your C tests, particularly if you have to set up and tear down a 158 test environment for your test programs, and it's useful to have them 159 all in the libtap library so that you only have to link your test 160 programs with one library. Rather than editing tap/basic.c and 161 tap/basic.h to add those additional functions, add additional *.c and 162 *.h files into the tap directory with the function implementations and 163 prototypes, and then add those additional objects to the library. 164 That way, you can update tap/basic.c and tap/basic.h from subsequent 165 releases of C TAP Harness without having to merge changes with your 166 own code. 167 168 Libraries of additional useful TAP test functions are available in 169 rra-c-util at: 170 171 <http://www.eyrie.org/~eagle/software/rra-c-util/> 172 173 Some of the code there is particularly useful when testing programs 174 that require Kerberos keys. 175 176 If you implement new test functions that compare an expected and seen 177 value, it's best to name them is_<something> and take the expected 178 value, the seen value, and then a printf-style format string and 179 possible arguments to match the calling convention of the functions 180 provided by C TAP Harness. 181 182 Shell 183 184 C TAP Harness provides a library of shell functions to make it easier 185 to write TAP tests in shell. That library includes much of the same 186 functionality as the C TAP library, but takes its parameters in a 187 somewhat different order to make better use of shell features. 188 189 The libtap.sh file should be installed in a directory named tap in 190 your test suite area. It can then be loaded by tests written in shell 191 using the environment set up by runtests with: 192 193 . "$SOURCE"/tap/libtap.sh 194 195 Here is a complete test case written in shell which produces the same 196 output as the TAP sample above: 197 198 #!/bin/sh 199 200 . "$SOURCE"/tap/libtap.sh 201 cd "$BUILD" 202 203 plan 4 204 ok 'the first test' true 205 ok '' [ 42 -eq 42 ] 206 diag a diagnostic, ignored by the harness 207 ok '' false 208 skip 'a skipped test' 209 210 The shell framework doesn't provide the is_* functions, so you'll use 211 the ok function more. It takes a string describing the text and then 212 treats all of its remaining arguments as a condition, evaluated the 213 same way as the arguments to the "if" statement. If that condition 214 evaluates to true, the test passes; otherwise, the test fails. 215 216 The plan, plan_lazy, diag, and bail functions work the same as with 217 the C library. skip takes a string and skips the next test with that 218 explanation. skip_block takes a count and a string and skips that 219 many tests with that explanation. skip_all takes an optional reason 220 and skips the entire test case. 221 222 Since it's common for shell programs to want to test the output of 223 commands, there's an additional function ok_program provided by the 224 shell test library. It takes the test description string, the 225 expected exit status, the expected program output, and then treats the 226 rest of its arguments as the program to run. That program is run with 227 standard error and standard output combined, and then its exit status 228 and output are tested against the provided values. 229 230 A utility function, strip_colon_error, is provided that runs the 231 command given as its arguments and strips text following a colon and a 232 space from the output (unless there is no whitespace on the line 233 before the colon and the space, normally indicating a prefix of the 234 program name). This function can be used to wrap commands that are 235 expected to fail with output that has a system- or locale-specific 236 error message appended, such as the output of strerror(). 237 238License 239 240 This file is part of the documentation of C TAP Harness, which can be 241 found at <http://www.eyrie.org/~eagle/software/c-tap-harness/>. 242 243 Copyright 2010 Russ Allbery <eagle@eyrie.org> 244 245 Copying and distribution of this file, with or without modification, 246 are permitted in any medium without royalty provided the copyright 247 notice and this notice are preserved. This file is offered as-is, 248 without any warranty. 249