https://github.com/akkartik/mu/blob/master/subx/003trace.cc

      1 //: The goal of layers is to make programs more easy to understand and more
      2 //: malleable, easy to rewrite in radical ways without accidentally breaking
      3 //: some corner case. Tests further both goals. They help understandability by
      4 //: letting one make small changes and get feedback. What if I wrote this line
      5 //: like so? What if I removed this function call, is it really necessary?
      6 //: Just try it, see if the tests pass. Want to explore rewriting this bit in
      7 //: this way? Tests put many refactorings on a firmer footing.
      8 //:
      9 //: But the usual way we write tests seems incomplete. Refactorings tend to
     10 //: work in the small, but don't help with changes to function boundaries. If
     11 //: you want to extract a new function you have to manually test-drive it to
     12 //: create tests for it. If you want to inline a function its tests are no
     13 //: longer valid. In both cases you end up having to reorganize code as well as
     14 //: tests, an error-prone activity.
     15 //:
     16 //: In response, this layer introduces the notion of domain-driven *white-box*
     17 //: testing. We focus on the domain of inputs the whole program needs to
     18 //: handle rather than the correctness of individual functions. All white-box
     19 //: tests invoke the program in a single way: by calling run() with some
     20 //: input. As the program operates on the input, it traces out a list of
     21 //: _facts_ deduced about the domain:
     22 //:   trace("label") << "fact 1: " << val;
     23 //:
     24 //: Tests can now check for these facts in the trace:
     25 //:   CHECK_TRACE_CONTENTS("label", "fact 1: 34\n"
     26 //:                                 "fact 2: 35\n");
     27 //:
     28 //: Since we never call anything but the run() function directly, we never have
     29 //: to rewrite the tests when we reorganize the internals of the program. We
     30 //: just have to make sure our rewrite deduces the same facts about the domain,
     31 //: and that's something we're going to have to do anyway.
     32 //:
     33 //: To avoid the combinatorial explosion of integration tests, each layer
     34 //: mainly logs facts to the trace with a common *label*. All tests in a layer
     35 //: tend to check facts with this label. Validating the facts logged with a
     36 //: specific label is like calling functions of that layer directly.
     37 //:
     38 //: To build robust tests, trace facts about your domain rather than details of
     39 //: how you computed them.
     40 //:
     41 //: More details: http://akkartik.name/blog/tracing-tests
     42 //:
     43 //: ---
     44 //:
     45 //: Between layers and domain-driven testing, programming starts to look like a
     46 //: fundamentally different activity. Instead of focusing on a) superficial,
     47 //: b) local rules on c) code [like say http://blog.bbv.ch/2013/06/05/clean-code-cheat-sheet],
     48 //: we allow programmers to engage with the a) deep, b) global structure of
     49 //: the c) domain. If you can systematically track discontinuities in the
     50 //: domain, you don't care if the code used gotos as long as it passed all
     51 //: tests. If tests become more robust to run, it becomes easier to try out
     52 //: radically different implementations for the same program. If code is
     53 //: super-easy to rewrite, it becomes less important what indentation style it
     54 //: uses, or that the objects are appropriately encapsulated, or that the
     55 //: functions are referentially transparent.
     56 //:
     57 //: Instead of plumbing, programming becomes building and gradually refining a
     58 //: map of the environment the program must operate under. Whether a program
     59 //: is 'correct' at a given point in time is a red herring; what matters is
     60 //: avoiding regression by monotonically nailing down the more 'eventful'
     61 //: parts of the terrain. It helps readers new and old, and rewards curiosity,
     62 //: to organize large programs in self-similar hierarchies of example tests
     63 //: colocated with the code that makes them work.
     64 //:
     65 //:   "Programming properly should be regarded as an activity by which
     66 //:   programmers form a mental model, rather than as production of a program."
     67 //:   -- Peter Naur (http://alistair.cockburn.us/ASD+book+extract%3A+%22Naur,+Ehn,+Musashi%22)
     68
     69 //:: == Core data structures
     70
     71 :(before "End Globals")
     72 trace_stream* Trace_stream = NULL;
     73
     74 :(before "End Types")
     75 struct trace_stream {
     76   vector<trace_line> past_lines;
     77   // End trace_stream Fields
     78
     79   trace_stream() {
     80     // End trace_stream Constructor
     81   }
     82   ~trace_stream() {
     83     // End trace_stream Destructor
     84   }
     85   // End trace_stream Methods
     86 };
     87
     88 //:: == Adding to the trace
     89
     90 //: Top-level method is trace() which can be used like an ostream. Usage:
     91 //:   trace(depth, label) << ... << end();
     92 //: Don't forget the 'end()' to actually append to the trace.
     93 :(before "End Includes")
     94 // No brackets around the expansion so that it prints nothing if Trace_stream
     95 // isn't initialized.
     96 #define trace(...)  !Trace_stream ? cerr : Trace_stream->stream(__VA_ARGS__)
     97
     98 :(before "End trace_stream Fields")
     99 // accumulator for current trace_line
    100 ostringstream* curr_stream;
    101 string curr_label;
    102 int curr_depth;
    103 // other stuff
    104 int collect_depth;  // avoid tracing lower levels for speed
    105 ofstream null_stream;  // never opened, so writes to it silently fail
    106
    107 //: Some constants.
    108 :(before "struct trace_stream")  // include constants in all cleaved compilation units
    109 const int Max_depth = 9999;
    110 :(before "End trace_stream Constructor")
    111 curr_stream = NULL;
    112 curr_depth = Max_depth;
    113 collect_depth = Max_depth;
    114
    115 :(before "struct trace_stream")
    116 struct trace_line {
    117   string contents;
    118   string label;
    119   int depth;  // 0 is 'sea level'; positive integers are progressively 'deeper' and lower level
    120   trace_line(string c, string l) {
    121     contents = c;
    122     label = l;
    123     depth = 0;
    124   }
    125   trace_line(string c, string l, int d) {
    126     contents = c;
    127     label = l;
    128     depth = d;
    129   }
    130 };
    131
    132 //: Starting a new trace line.
    133 :(before "End trace_stream Methods")
    134 ostream& stream(string label) {
    135   return stream(Max_depth, label);
    136 }
    137
    138 ostream& stream(int depth, string label) {
    139   if (depth > collect_depth) return null_stream;
    140   curr_stream = new ostringstream;
    141   curr_label = label;
    142   curr_depth = depth;
    143   (*curr_stream) << std::hex;  // printing addresses is the common case
    144   return *curr_stream;
    145 }
    146
    147 //: End of a trace line; append it to the trace.
    148 :(before "End Types")
    149 struct end {};
    150 :(code)
    151 ostream& operator<<(ostream& os, end /*unused*/) {
    152   if (Trace_stream) Trace_stream->newline();
    153   return os;
    154 }
    155
    156 :(before "End trace_stream Methods")
    157 void newline();
    158 :(code)
    159 void trace_stream::newline() {
    160   if (!curr_stream) return;
    161   string curr_contents = curr_stream->str();
    162   if (!curr_contents.empty()) {
    163     past_lines.push_back(trace_line(curr_contents, trim(curr_label), curr_depth));  // preserve indent in contents
    164     // maybe incrementally dump trace
    165     trace_line& t = past_lines.back();
    166     if (should_incrementally_print_trace()) {
    167       cerr       << std::setw(4) << t.depth << ' ' << t.label << ": " << t.contents << '\n';
    168     }
    169     // End trace Commit
    170   }
    171
    172   // clean up
    173   delete curr_stream;
    174   curr_stream = NULL;
    175   curr_label.clear();
    176   curr_depth = Max_depth;
    177 }
    178
    179 //:: == Initializing the trace in tests
    180
    181 :(before "End Includes")
    182 #define START_TRACING_UNTIL_END_OF_SCOPE  lease_tracer leased_tracer;
    183 :(before "End Test Setup")
    184 START_TRACING_UNTIL_END_OF_SCOPE
    185
    186 //: Trace_stream is a resource, lease_tracer uses RAII to manage it.
    187 :(before "End Types")
    188 struct lease_tracer {
    189   lease_tracer();
    190   ~lease_tracer();
    191 };
    192 :(code)
    193 lease_tracer::lease_tracer() { Trace_stream = new trace_stream; }
    194 lease_tracer::~lease_tracer() {
    195   delete Trace_stream;
    196   Trace_stream = NULL;
    197 }
    198
    199 //:: == Errors and warnings using traces
    200
    201 :(before "End Includes")
    202 #define raise  (!Trace_stream ? (++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Error_depth, "error"))
    203 #define warn (!Trace_stream ? (++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Warn_depth, "warn"))
    204
    205 //: Print errors and warnings to the screen by default.
    206 :(before "struct trace_stream")  // include constants in all cleaved compilation units
    207 const int Error_depth = 0;
    208 const int Warn_depth = 1;
    209 :(before "End Globals")
    210 int Hide_errors = false;  // if set, don't print errors or warnings to screen
    211 int Hide_warnings = false;  // if set, don't print warnings to screen
    212 :(before "End Reset")
    213 Hide_errors = false;
    214 Hide_warnings = false;
    215 //: Never dump warnings in tests
    216 :(before "End Test Setup")
    217 Hide_warnings = true;
    218 :(code)
    219 bool trace_stream::should_incrementally_print_trace() {
    220   if (!Hide_errors && curr_depth == Error_depth) return true;
    221   if (!Hide_warnings && !Hide_errors && curr_depth == Warn_depth) return true;
    222   // End Incremental Trace Print Conditions
    223   return false;
    224 }
    225 :(before "End trace_stream Methods")
    226 bool should_incrementally_print_trace();
    227
    228 :(before "End Globals")
    229 int Trace_errors = 0;  // used only when Trace_stream is NULL
    230
    231 // Fail tests that displayed (unexpected) errors.
    232 // Expected errors should always be hidden and silently checked for.
    233 :(before "End Test Teardown")
    234 if (Passed && !Hide_errors && trace_contains_errors()) {
    235   Passed = false;
    236 }
    237 :(code)
    238 bool trace_contains_errors() {
    239   return Trace_errors > 0 || trace_count("error") > 0;
    240 }
    241
    242 :(before "End Includes")
    243 // If we aren't yet sure how to deal with some corner case, use assert_for_now
    244 // to indicate that it isn't an inviolable invariant.
    245 #define assert_for_now assert
    246 #define raise_for_now raise
    247
    248 //:: == Other assertions on traces
    249 //: Primitives:
    250 //:   - CHECK_TRACE_CONTENTS(lines)
    251 //:     Assert that the trace contains the given lines (separated by newlines)
    252 //:     in order. There can be other intervening lines between them.
    253 //:   - CHECK_TRACE_DOESNT_CONTAIN(line)
    254 //:   - CHECK_TRACE_DOESNT_CONTAIN(label, contents)
    255 //:     Assert that the trace doesn't contain the given (single) line.
    256 //:   - CHECK_TRACE_COUNT(label, count)
    257 //:     Assert that the trace contains exactly 'count' lines with the given
    258 //:     'label'.
    259 //:   - CHECK_TRACE_CONTAINS_ERRORS()
    260 //:   - CHECK_TRACE_DOESNT_CONTAIN_ERRORS()
    261 //:   - trace_count_prefix(label, prefix)
    262 //:     Count the number of trace lines with the given 'label' that start with
    263 //:     the given 'prefix'.
    264
    265 :(before "End Includes")
    266 #define CHECK_TRACE_CONTENTS(...)  check_trace_contents(__FUNCTION__, __FILE__, __LINE__, __VA_ARGS__)
    267
    268 #define CHECK_TRACE_DOESNT_CONTAIN(...)  CHECK(trace_doesnt_contain(__VA_ARGS__))
    269
    270 #define CHECK_TRACE_COUNT(label, count) \
    271   if (Passed && trace_count(label) != (count)) { \
    272     cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): trace_count of " << label << " should be " << count << '\n'; \
    273     cerr << "  got " << trace_count(label) << '\n';  /* multiple eval */ \
    274     DUMP(label); \
    275     Passed = false; \
    276     return;  /* Currently we stop at the very first failure. */ \
    277   }
    278
    279 #define CHECK_TRACE_CONTAINS_ERRORS()  CHECK(trace_contains_errors())
    280 #define CHECK_TRACE_DOESNT_CONTAIN_ERRORS() \
    281   if (Passed && trace_contains_errors()) { \
    282     cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): unexpected errors\n"; \
    283     DUMP("error"); \
    284     Passed = false; \
    285     return; \
    286   }
    287
    288 // Allow tests to ignore trace lines generated during setup.
    289 #define CLEAR_TRACE  delete Trace_stream, Trace_stream = new trace_stream
    290
    291 :(code)
    292 bool check_trace_contents(string FUNCTION, string FILE, int LINE, string expected) {
    293   if (!Passed) return false;
    294   if (!Trace_stream) return false;
    295   vector<string> expected_lines = split(expected, "\n");
    296   int curr_expected_line = 0;
    297   while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
    298     ++curr_expected_line;
    299   if (curr_expected_line == SIZE(expected_lines)) return true;
    300   string label, contents;
    301   split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
    302   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
    303     if (label != p->label) continue;
    304     if (contents != trim(p->contents)) continue;
    305     ++curr_expected_line;
    306     while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
    307       ++curr_expected_line;
    308     if (curr_expected_line == SIZE(expected_lines)) return true;
    309     split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
    310   }
    311
    312   if (line_exists_anywhere(label, contents)) {
    313     cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): line [" << label << ": " << contents << "] out of order in trace:\n";
    314     DUMP("");
    315   }
    316   else {
    317     cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): missing [" << contents << "] in trace:\n";
    318     DUMP(label);
    319   }
    320   Passed = false;
    321   return false;
    322 }
    323
    324 bool trace_doesnt_contain(string expected) {
    325   vector<string> tmp = split_first(expected, ": ");
    326   if (SIZE(tmp) == 1) {
    327     raise << expected << ": missing label or contents in trace line\n" << end();
    328     assert(false);
    329   }
    330   return trace_count(tmp.at(0), tmp.at(1)) == 0;
    331 }
    332
    333 int trace_count(string label) {
    334   return trace_count(label, "");
    335 }
    336
    337 int trace_count(string label, string line) {
    338   if (!Trace_stream) return 0;
    339   long result = 0;
    340   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
    341     if (label == p->label) {
    342       if (line == "" || trim(line) == trim(p->contents))
    343         ++result;
    344     }
    345   }
    346   return result;
    347 }
    348
    349 int trace_count_prefix(string label, string prefix) {
    350   if (!Trace_stream) return 0;
    351   long result = 0;
    352   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
    353     if (label == p->label) {
    354       if (starts_with(trim(p->contents), trim(prefix)))
    355         ++result;
    356     }
    357   }
    358   return result;
    359 }
    360
    361 void split_label_contents(const string& s, string* label, string* contents) {
    362   static const string delim(": ");
    363   size_t pos = s.find(delim);
    364   if (pos == string::npos) {
    365     *label = "";
    366     *contents = trim(s);
    367   }
    368   else {
    369     *label = trim(s.substr(0, pos));
    370     *contents = trim(s.substr(pos+SIZE(delim)));
    371   }
    372 }
    373
    374 bool line_exists_anywhere(const string& label, const string& contents) {
    375   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
    376     if (label != p->label) continue;
    377     if (contents == trim(p->contents)) return true;
    378   }
    379   return false;
    380 }
    381
    382 vector<string> split(string s, string delim) {
    383   vector<string> result;
    384   size_t begin=0, end=s.find(delim);
    385   while (true) {
    386     if (end == string::npos) {
    387       result.push_back(string(s, begin, string::npos));
    388       break;
    389     }
    390     result.push_back(string(s, begin, end-begin));
    391     begin = end+SIZE(delim);
    392     end = s.find(delim, begin);
    393   }
    394   return result;
    395 }
    396
    397 vector<string> split_first(string s, string delim) {
    398   vector<string> result;
    399   size_t end=s.find(delim);
    400   result.push_back(string(s, 0, end));
    401   if (end != string::npos)
    402     result.push_back(string(s, end+SIZE(delim), string::npos));
    403   return result;
    404 }
    405
    406 //:: == Helpers for debugging using traces
    407
    408 :(before "End Includes")
    409 // To debug why a test is failing, dump its trace using '?'.
    410 #define DUMP(label)  if (Trace_stream) cerr << Trace_stream->readable_contents(label);
    411
    412 // To add temporary prints to the trace, use 'dbg'.
    413 // `git log` should never show any calls to 'dbg'.
    414 #define dbg trace(0, "a")
    415
    416 //: Dump the entire trace to file where it can be browsed offline.
    417 //: Dump the trace as it happens; that way you get something even if the
    418 //: program crashes.
    419
    420 :(before "End Globals")
    421 ofstream Trace_file;
    422 :(before "End Commandline Options(*arg)")
    423 else if (is_equal(*arg, "--trace")) {
    424   cerr << "saving trace to 'last_run'\n";
    425   Trace_file.open("last_run");
    426   // Add a dummy line up top; otherwise the `browse_trace` tool currently has
    427   // no way to expand any lines above an error.
    428   Trace_file << "   0 dummy: start\n";
    429 }
    430 :(before "End trace Commit")
    431 if (Trace_file) {
    432   Trace_file << std::setw(4) << t.depth << ' ' << t.label << ": " << t.contents << '\n';
    433 }
    434 :(before "End One-time Setup")
    435 atexit(cleanup_main);
    436 :(code)
    437 void cleanup_main() {
    438   if (Trace_file) Trace_file.close();
    439   // End cleanup_main
    440 }
    441
    442 :(before "End trace_stream Methods")
    443 string readable_contents(string label) {
    444   string trim(const string& s);  // prototype
    445   ostringstream output;
    446   label = trim(label);
    447   for (vector<trace_line>::iterator p = past_lines.begin();  p != past_lines.end();  ++p)
    448     if (label.empty() || label == p->label)
    449       output << std::setw(4) << p->depth << ' ' << p->label << ": " << p->contents << '\n';
    450   return output.str();
    451 }
    452
    453 //: Print traces to the screen as they happen.
    454 //: Particularly useful when juggling multiple trace streams, like when
    455 //: debugging sandboxes.
    456 :(before "End Globals")
    457 bool Dump_trace = false;
    458 :(before "End Commandline Options(*arg)")
    459 else if (is_equal(*arg, "--dump")) {
    460   Dump_trace = true;
    461 }
    462 :(before "End Incremental Trace Print Conditions")
    463 if (Dump_trace) return true;
    464
    465 //: Miscellaneous helpers.
    466
    467 :(code)
    468 string trim(const string& s) {
    469   string::const_iterator first = s.begin();
    470   while (first != s.end() && isspace(*first))
    471     ++first;
    472   if (first == s.end()) return "";
    473
    474   string::const_iterator last = --s.end();
    475   while (last != s.begin() && isspace(*last))
    476     --last;
    477   ++last;
    478   return string(first, last);
    479 }
    480
    481 :(before "End Includes")
    482 #include <vector>
    483 using std::vector;
    484 #include <list>
    485 using std::list;
    486 #include <set>
    487 using std::set;
    488
    489 #include <sstream>
    490 using std::istringstream;
    491 using std::ostringstream;
    492
    493 #include <fstream>
    494 using std::ifstream;
    495 using std::ofstream;