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;