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 string unescape_newline(string& s) {
133   std::stringstream ss;
134   for (int i = 0;  i < SIZE(s);  ++i) {
135     if (s.at(i) == '\n')
136       ss << "\\n";
137     else
138       ss << s.at(i);
139   }
140   return ss.str();
141 }
142 
143 void dump_trace_line(ostream& s, trace_line& t) {
144   s << std::setw(4) << t.depth << ' ' << t.label << ": " << unescape_newline(t.contents) << '\n';
145 }
146 
147 //: Starting a new trace line.
148 :(before "End trace_stream Methods")
149 ostream& stream(string label) {
150   return stream(Max_depth, label);
151 }
152 
153 ostream& stream(int depth, string label) {
154   if (depth > collect_depth) return null_stream;
155   curr_stream = new ostringstream;
156   curr_label = label;
157   curr_depth = depth;
158   (*curr_stream) << std::hex;  // printing addresses is the common case
159   return *curr_stream;
160 }
161 
162 //: End of a trace line; append it to the trace.
163 :(before "End Types")
164 struct end {};
165 :(code)
166 ostream& operator<<(ostream& os, end /*unused*/) {
167   if (Trace_stream) Trace_stream->newline();
168   return os;
169 }
170 
171 //: Fatal error.
172 :(before "End Types")
173 struct die {};
174 :(code)
175 ostream& operator<<(ostream& /*unused*/, die /*unused*/) {
176   if (Trace_stream) Trace_stream->newline();
177   exit(1);
178 }
179 
180 :(before "End trace_stream Methods")
181 void newline();
182 :(code)
183 void trace_stream::newline() {
184   if (!curr_stream) return;
185   string curr_contents = curr_stream->str();
186   if (!curr_contents.empty()) {
187     past_lines.push_back(trace_line(curr_contents, trim(curr_label), curr_depth));  // preserve indent in contents
188     // maybe incrementally dump trace
189     trace_line& t = past_lines.back();
190     if (should_incrementally_print_trace()) {
191       dump_trace_line(cerr, t);
192     }
193     // End trace Commit
194   }
195 
196   // clean up
197   delete curr_stream;
198   curr_stream = NULL;
199   curr_label.clear();
200   curr_depth = Max_depth;
201 }
202 
203 //:: == Initializing the trace in tests
204 
205 :(before "End Includes")
206 #define START_TRACING_UNTIL_END_OF_SCOPE  lease_tracer leased_tracer;
207 :(before "End Test Setup")
208 START_TRACING_UNTIL_END_OF_SCOPE
209 
210 //: Trace_stream is a resource, lease_tracer uses RAII to manage it.
211 :(before "End Types")
212 struct lease_tracer {
213   lease_tracer();
214   ~lease_tracer();
215 };
216 :(code)
217 lease_tracer::lease_tracer() { Trace_stream = new trace_stream; }
218 lease_tracer::~lease_tracer() {
219   delete Trace_stream;
220   Trace_stream = NULL;
221 }
222 
223 //:: == Errors and warnings using traces
224 
225 :(before "End Includes")
226 #define raise  (!Trace_stream ? (++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Error_depth, "error"))
227 #define warn (!Trace_stream ? (++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Warn_depth, "warn"))
228 
229 //: Print errors and warnings to the screen by default.
230 :(before "struct trace_stream")  // include constants in all cleaved compilation units
231 const int Error_depth = 0;
232 const int Warn_depth = 1;
233 :(before "End Globals")
234 int Hide_errors = false;  // if set, don't print errors or warnings to screen
235 int Hide_warnings = false;  // if set, don't print warnings to screen
236 :(before "End Reset")
237 Hide_errors = false;
238 Hide_warnings = false;
239 //: Never dump warnings in tests
240 :(before "End Test Setup")
241 Hide_warnings = true;
242 :(code)
243 bool trace_stream::should_incrementally_print_trace() {
244   if (!Hide_errors && curr_depth == Error_depth) return true;
245   if (!Hide_warnings && !Hide_errors && curr_depth == Warn_depth) return true;
246   // End Incremental Trace Print Conditions
247   return false;
248 }
249 :(before "End trace_stream Methods")
250 bool should_incrementally_print_trace();
251 
252 :(before "End Globals")
253 int Trace_errors = 0;  // used only when Trace_stream is NULL
254 
255 // Fail tests that displayed (unexpected) errors.
256 // Expected errors should always be hidden and silently checked for.
257 :(before "End Test Teardown")
258 if (Passed && !Hide_errors && trace_contains_errors()) {
259   Passed = false;
260 }
261 :(code)
262 bool trace_contains_errors() {
263   return Trace_errors > 0 || trace_count("error") > 0;
264 }
265 
266 :(before "End Includes")
267 // If we aren't yet sure how to deal with some corner case, use assert_for_now
268 // to indicate that it isn't an inviolable invariant.
269 #define assert_for_now assert
270 #define raise_for_now raise
271 
272 //:: == Other assertions on traces
273 //: Primitives:
274 //:   - CHECK_TRACE_CONTENTS(lines)
275 //:     Assert that the trace contains the given lines (separated by newlines)
276 //:     in order. There can be other intervening lines between them.
277 //:   - CHECK_TRACE_DOESNT_CONTAIN(line)
278 //:   - CHECK_TRACE_DOESNT_CONTAIN(label, contents)
279 //:     Assert that the trace doesn't contain the given (single) line.
280 //:   - CHECK_TRACE_COUNT(label, count)
281 //:     Assert that the trace contains exactly 'count' lines with the given
282 //:     'label'.
283 //:   - CHECK_TRACE_CONTAINS_ERRORS()
284 //:   - CHECK_TRACE_DOESNT_CONTAIN_ERRORS()
285 //:   - trace_count_prefix(label, prefix)
286 //:     Count the number of trace lines with the given 'label' that start with
287 //:     the given 'prefix'.
288 
289 :(before "End Includes")
290 #define CHECK_TRACE_CONTENTS(...)  check_trace_contents(__FUNCTION__, __FILE__, __LINE__, __VA_ARGS__)
291 
292 #define CHECK_TRACE_DOESNT_CONTAIN(...)  CHECK(trace_doesnt_contain(__VA_ARGS__))
293 
294 #define CHECK_TRACE_COUNT(label, count) \
295   if (Passed && trace_count(label) != (count)) { \
296     cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): trace_count of " << label << " should be " << count << '\n'; \
297     cerr << "  got " << trace_count(label) << '\n';  /* multiple eval */ \
298     DUMP(label); \
299     Passed = false; \
300     return;  /* Currently we stop at the very first failure. */ \
301   }
302 
303 #define CHECK_TRACE_CONTAINS_ERRORS()  CHECK(trace_contains_errors())
304 #define CHECK_TRACE_DOESNT_CONTAIN_ERRORS() \
305   if (Passed && trace_contains_errors()) { \
306     cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): unexpected errors\n"; \
307     DUMP("error"); \
308     Passed = false; \
309     return; \
310   }
311 
312 // Allow tests to ignore trace lines generated during setup.
313 #define CLEAR_TRACE  delete Trace_stream, Trace_stream = new trace_stream
314 
315 :(code)
316 bool check_trace_contents(string FUNCTION, string FILE, int LINE, string expected) {
317   if (!Passed) return false;
318   if (!Trace_stream) return false;
319   vector<string> expected_lines = split(expected, "\n");
320   int curr_expected_line = 0;
321   while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
322     ++curr_expected_line;
323   if (curr_expected_line == SIZE(expected_lines)) return true;
324   string label, contents;
325   split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
326   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
327     if (label != p->label) continue;
328     string t = trim(p->contents);
329     if (contents != unescape_newline(t)) continue;
330     ++curr_expected_line;
331     while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
332       ++curr_expected_line;
333     if (curr_expected_line == SIZE(expected_lines)) return true;
334     split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
335   }
336 
337   if (line_exists_anywhere(label, contents)) {
338     cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): line [" << label << ": " << contents << "] out of order in trace:\n";
339     DUMP("");
340   }
341   else {
342     cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): missing [" << contents << "] in trace:\n";
343     DUMP(label);
344   }
345   Passed = false;
346   return false;
347 }
348 
349 bool trace_doesnt_contain(string expected) {
350   vector<string> tmp = split_first(expected, ": ");
351   if (SIZE(tmp) == 1) {
352     raise << expected << ": missing label or contents in trace line\n" << end();
353     assert(false);
354   }
355   return trace_count(tmp.at(0), tmp.at(1)) == 0;
356 }
357 
358 int trace_count(string label) {
359   return trace_count(label, "");
360 }
361 
362 int trace_count(string label, string line) {
363   if (!Trace_stream) return 0;
364   long result = 0;
365   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
366     if (label == p->label) {
367       if (line == "" || trim(line) == trim(p->contents))
368         ++result;
369     }
370   }
371   return result;
372 }
373 
374 int trace_count_prefix(string label, string prefix) {
375   if (!Trace_stream) return 0;
376   long result = 0;
377   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
378     if (label == p->label) {
379       if (starts_with(trim(p->contents), trim(prefix)))
380         ++result;
381     }
382   }
383   return result;
384 }
385 
386 void split_label_contents(const string& s, string* label, string* contents) {
387   static const string delim(": ");
388   size_t pos = s.find(delim);
389   if (pos == string::npos) {
390     *label = "";
391     *contents = trim(s);
392   }
393   else {
394     *label = trim(s.substr(0, pos));
395     *contents = trim(s.substr(pos+SIZE(delim)));
396   }
397 }
398 
399 bool line_exists_anywhere(const string& label, const string& contents) {
400   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
401     if (label != p->label) continue;
402     if (contents == trim(p->contents)) return true;
403   }
404   return false;
405 }
406 
407 vector<string> split(string s, string delim) {
408   vector<string> result;
409   size_t begin=0, end=s.find(delim);
410   while (true) {
411     if (end == string::npos) {
412       result.push_back(string(s, begin, string::npos));
413       break;
414     }
415     result.push_back(string(s, begin, end-begin));
416     begin = end+SIZE(delim);
417     end = s.find(delim, begin);
418   }
419   return result;
420 }
421 
422 vector<string> split_first(string s, string delim) {
423   vector<string> result;
424   size_t end=s.find(delim);
425   result.push_back(string(s, 0, end));
426   if (end != string::npos)
427     result.push_back(string(s, end+SIZE(delim), string::npos));
428   return result;
429 }
430 
431 //:: == Helpers for debugging using traces
432 
433 :(before "End Includes")
434 // To debug why a test is failing, dump its trace using '?'.
435 #define DUMP(label)  if (Trace_stream) cerr << Trace_stream->readable_contents(label);
436 
437 // To add temporary prints to the trace, use 'dbg'.
438 // `git log` should never show any calls to 'dbg'.
439 #define dbg trace(0, "a")
440 
441 //: Dump the entire trace to file where it can be browsed offline.
442 //: Dump the trace as it happens; that way you get something even if the
443 //: program crashes.
444 
445 :(before "End Globals")
446 ofstream Trace_file;
447 :(before "End Commandline Options(*arg)")
448 else if (is_equal(*arg, "--trace")) {
449   cerr << "saving trace to 'last_run'\n";
450   Trace_file.open("last_run");
451   // Add a dummy line up top; otherwise the `browse_trace` tool currently has
452   // no way to expand any lines above an error.
453   Trace_file << "   0 dummy: start\n";
454 }
455 :(before "End trace Commit")
456 if (Trace_file) {
457   dump_trace_line(Trace_file, t);
458 }
459 :(before "End One-time Setup")
460 atexit(cleanup_main);
461 :(code)
462 void cleanup_main() {
463   if (Trace_file) Trace_file.close();
464   // End cleanup_main
465 }
466 
467 :(before "End trace_stream Methods")
468 string readable_contents(string label) {
469   string trim(const string& s);  // prototype
470   ostringstream output;
471   label = trim(label);
472   for (vector<trace_line>::iterator p = past_lines.begin();  p != past_lines.end();  ++p)
473     if (label.empty() || label == p->label)
474       dump_trace_line(output, *p);
475   return output.str();
476 }
477 
478 //: Print traces to the screen as they happen.
479 //: Particularly useful when juggling multiple trace streams, like when
480 //: debugging sandboxes.
481 :(before "End Globals")
482 bool Dump_trace = false;
483 :(before "End Commandline Options(*arg)")
484 else if (is_equal(*arg, "--dump")) {
485   Dump_trace = true;
486 }
487 :(before "End Incremental Trace Print Conditions")
488 if (Dump_trace) return true;
489 
490 //: Miscellaneous helpers.
491 
492 :(code)
493 string trim(const string& s) {
494   string::const_iterator first = s.begin();
495   while (first != s.end() && isspace(*first))
496     ++first;
497   if (first == s.end()) return "";
498 
499   string::const_iterator last = --s.end();
500   while (last != s.begin() && isspace(*last))
501     --last;
502   ++last;
503   return string(first, last);
504 }
505 
506 :(before "End Includes")
507 #include <vector>
508 using std::vector;
509 #include <list>
510 using std::list;
511 #include <set>
512 using std::set;
513 
514 #include <sstream>
515 using std::istringstream;
516 using std::ostringstream;
517 
518 #include <fstream>
519 using std::ifstream;
520 using std::ofstream;