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