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* testing.
 17 //: We focus on the domain of inputs the whole program needs to handle rather
 18 //: than the correctness of individual functions. All tests invoke the program
 19 //: in a single way: by calling run() with some input. As the program operates
 20 //: on the input, it traces out a list of _facts_ deduced about the domain:
 21 //:   trace("label") << "fact 1: " << val;
 22 //:
 23 //: Tests can now check these facts:
 24 //:   :(scenario foo)
 25 //:   34  # call run() with this input
 26 //:   +label: fact 1: 34  # 'run' should have deduced this fact
 27 //:   -label: fact 1: 35  # the trace should not contain such a fact
 28 //:
 29 //: Since we never call anything but the run() function directly, we never have
 30 //: to rewrite the tests when we reorganize the internals of the program. We
 31 //: just have to make sure our rewrite deduces the same facts about the domain,
 32 //: and that's something we're going to have to do anyway.
 33 //:
 34 //: To avoid the combinatorial explosion of integration tests, each layer
 35 //: mainly logs facts to the trace with a common *label*. All tests in a layer
 36 //: tend to check facts with this label. Validating the facts logged with a
 37 //: specific label is like calling functions of that layer directly.
 38 //:
 39 //: To build robust tests, trace facts about your domain rather than details of
 40 //: how you computed them.
 41 //:
 42 //: More details: http://akkartik.name/blog/tracing-tests
 43 //:
 44 //: ---
 45 //:
 46 //: Between layers and domain-driven testing, programming starts to look like a
 47 //: fundamentally different activity. Instead of a) superficial, b) local rules
 48 //: on c) code [like say http://blog.bbv.ch/2013/06/05/clean-code-cheat-sheet],
 49 //: we allow programmers to engage with the a) deep, b) global structure of the
 50 //: c) domain. If you can systematically track discontinuities in the domain,
 51 //: you don't care if the code used gotos as long as it passed the tests. If
 52 //: tests become more robust to run it becomes easier to try out radically
 53 //: different implementations for the same program. If code is super-easy to
 54 //: rewrite, it becomes less important what indentation style it uses, or that
 55 //: the objects are appropriately encapsulated, or that the functions are
 56 //: referentially transparent.
 57 //:
 58 //: Instead of plumbing, programming becomes building and gradually refining a
 59 //: map of the environment the program must operate under. Whether a program is
 60 //: 'correct' at a given point in time is a red herring; what matters is
 61 //: avoiding regression by monotonically nailing down the more 'eventful' parts
 62 //: of the terrain. It helps readers new and old, and rewards curiosity, to
 63 //: organize large programs in self-similar hierarchies of example scenarios
 64 //: colocated with the code that makes them work.
 65 //:
 66 //:   "Programming properly should be regarded as an activity by which
 67 //:   programmers form a mental model, rather than as production of a program."
 68 //:   -- Peter Naur (http://alistair.cockburn.us/ASD+book+extract%3A+%22Naur,+Ehn,+Musashi%22)
 69 
 70 :(before "End Types")
 71 struct trace_line {
 72   int depth;  // optional field just to help browse traces later
 73   string label;
 74   string contents;
 75   trace_line(string l, string c) :depth(0), label(l), contents(c) {}
 76   trace_line(int d, string l, string c) :depth(d), label(l), contents(c) {}
 77 };
 78 
 79 //: Support for tracing an entire run.
 80 //: Traces can have a lot of overhead, so only turn them on when asked.
 81 :(before "End Commandline Options(*arg)")
 82 else if (is_equal(*arg, "--trace")) {
 83   Save_trace = true;
 84 }
 85 :(before "End Commandline Parsing")
 86 if (Save_trace) {
 87   cerr << "initializing trace\n";
 88   Trace_stream = new trace_stream;
 89 }
 90 :(code)
 91 void cleanup_main() {
 92   if (!Trace_stream) return;
 93   if (Save_trace)
 94     Trace_stream->save();
 95   delete Trace_stream;
 96   Trace_stream = NULL;
 97 }
 98 :(before "End One-time Setup")
 99 atexit(cleanup_main);
100 
101 :(before "End Types")
102 // Pre-define some global constants that trace_stream needs to know about.
103 // Since they're in the Types section, they'll be included in any cleaved
104 // compilation units. So no extern linkage.
105 const int Max_depth = 9999;
106 const int Error_depth = 0;  // definitely always print errors
107 const int Warn_depth = 1;
108 
109 struct trace_stream {
110   vector<trace_line> past_lines;
111   // accumulator for current line
112   ostringstream* curr_stream;
113   string curr_label;
114   int curr_depth;
115   int collect_depth;
116   ofstream null_stream;  // never opens a file, so writes silently fail
117   trace_stream() :curr_stream(NULL), curr_depth(Max_depth), collect_depth(Max_depth) {}
118   ~trace_stream() { if (curr_stream) delete curr_stream; }
119 
120   ostream& stream(string label) {
121     return stream(Max_depth, label);
122   }
123 
124   ostream& stream(int depth, string label) {
125     if (depth > collect_depth) return null_stream;
126     curr_stream = new ostringstream;
127     curr_label = label;
128     curr_depth = depth;
129     (*curr_stream) << std::hex;
130     return *curr_stream;
131   }
132 
133   void save() {
134     cerr << "saving trace to 'last_run'\n";
135     ofstream fout("last_run");
136     fout << readable_contents("");
137     fout.close();
138   }
139 
140   // be sure to call this before messing with curr_stream or curr_label
141   void newline();
142   // useful for debugging
143   string readable_contents(string label);  // empty label = show everything
144 };
145 
146 :(code)
147 void trace_stream::newline() {
148   if (!curr_stream) return;
149   string curr_contents = curr_stream->str();
150   if (!curr_contents.empty()) {
151     past_lines.push_back(trace_line(curr_depth, trim(curr_label), curr_contents));  // preserve indent in contents
152     if ((!Hide_errors && curr_depth == Error_depth)
153         || (!Hide_warnings && !Hide_errors && curr_depth == Warn_depth)
154         || Dump_trace
155         || (!Dump_label.empty() && curr_label == Dump_label))
156       cerr << curr_label << ": " << curr_contents << '\n';
157   }
158   delete curr_stream;
159   curr_stream = NULL;
160   curr_label.clear();
161   curr_depth = Max_depth;
162 }
163 
164 string trace_stream::readable_contents(string label) {
165   ostringstream output;
166   label = trim(label);
167   for (vector<trace_line>::iterator p = past_lines.begin();  p != past_lines.end();  ++p)
168     if (label.empty() || label == p->label)
169       output << std::setw(4) << p->depth << ' ' << p->label << ": " << p->contents << '\n';
170   return output.str();
171 }
172 
173 :(before "End Globals")
174 trace_stream* Trace_stream = NULL;
175 int Trace_errors = 0;  // used only when Trace_stream is NULL
176 
177 //: option to print trace to the screen
178 :(before "End Globals")
179 bool Flag_dump_trace = false;
180 :(before "End Commandline Options(*arg)")
181 else if (is_equal(*arg, "--dump")) {
182   Flag_dump_trace = true;
183 }
184 
185 :(before "End Globals")
186 bool Hide_errors = false;  // if set, don't print even error trace lines to screen
187 bool Hide_warnings = false;  // if set, don't print warnings to screen
188 bool Dump_trace = false;  // if set, print trace lines to screen
189 string Dump_label = "";  // if set, print trace lines matching a single label to screen
190 :(before "End Reset")
191 Hide_errors = false;
192 Hide_warnings = false;
193 Dump_trace = Flag_dump_trace;
194 Dump_label = "";
195 //: Never dump warnings in scenarios
196 :(before "End Test Setup")
197 Hide_warnings = true;
198 
199 :(before "End Includes")
200 #define CLEAR_TRACE  delete Trace_stream, Trace_stream = new trace_stream;
201 
202 // Top-level helper. IMPORTANT: can't nest
203 #define trace(...)  !Trace_stream ? cerr /*print nothing*/ : Trace_stream->stream(__VA_ARGS__)
204 
205 // Just for debugging; 'git log' should never show any calls to 'dbg'.
206 #define dbg trace(0, "a")
207 #define DUMP(label)  if (Trace_stream) cerr << Trace_stream->readable_contents(label);
208 
209 // Errors and warnings are special layers.
210 #define raise  (!Trace_stream ? (++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Error_depth, "error"))
211 #define warn (!Trace_stream ? (++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Warn_depth, "warn"))
212 // If we aren't yet sure how to deal with some corner case, use assert_for_now
213 // to indicate that it isn't an inviolable invariant.
214 #define assert_for_now assert
215 #define raise_for_now raise
216 
217 // Inside tests, fail any tests that displayed (unexpected) errors.
218 // Expected errors in tests should always be hidden and silently checked for.
219 :(before "End Test Teardown")
220 if (Passed && !Hide_errors && trace_contains_errors()) {
221   Passed = false;
222 }
223 :(code)
224 bool trace_contains_errors() {
225   return Trace_errors > 0 || trace_count("error") > 0;
226 }
227 
228 :(before "End Types")
229 struct end {};
230 :(code)
231 ostream& operator<<(ostream& os, end /*unused*/) {
232   if (Trace_stream) Trace_stream->newline();
233   return os;
234 }
235 
236 :(before "End Globals")
237 bool Save_trace = false;  // if set, write out trace to disk
238 
239 // Trace_stream is a resource, lease_tracer uses RAII to manage it.
240 :(before "End Types")
241 struct lease_tracer {
242   lease_tracer();
243   ~lease_tracer();
244 };
245 :(code)
246 lease_tracer::lease_tracer() { Trace_stream = new trace_stream; }
247 lease_tracer::~lease_tracer() {
248   if (Save_trace) Trace_stream->save();
249   delete Trace_stream, Trace_stream = NULL;
250 }
251 :(before "End Includes")
252 #define START_TRACING_UNTIL_END_OF_SCOPE  lease_tracer leased_tracer;
253 :(before "End Test Setup")
254 START_TRACING_UNTIL_END_OF_SCOPE
255 
256 :(before "End Includes")
257 #define CHECK_TRACE_CONTENTS(...)  check_trace_contents(__FUNCTION__, __FILE__, __LINE__, __VA_ARGS__)
258 
259 #define CHECK_TRACE_CONTAINS_ERRORS()  CHECK(trace_contains_errors())
260 #define CHECK_TRACE_DOESNT_CONTAIN_ERRORS() \
261   if (Passed && trace_contains_errors()) { \
262     cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): unexpected errors\n"; \
263     DUMP("error"); \
264     Passed = false; \
265     return; \
266   }
267 
268 #define CHECK_TRACE_COUNT(label, count) \
269   if (Passed && trace_count(label) != (count)) { \
270     cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): trace_count of " << label << " should be " << count << '\n'; \
271     cerr << "  got " << trace_count(label) << '\n';  /* multiple eval */ \
272     DUMP(label); \
273     Passed = false; \
274     return;  /* Currently we stop at the very first failure. */ \
275   }
276 
277 #define CHECK_TRACE_DOESNT_CONTAIN(...)  CHECK(trace_doesnt_contain(__VA_ARGS__))
278 
279 :(code)
280 bool check_trace_contents(string FUNCTION, string FILE, int LINE, string expected) {
281   if (!Passed) return false;
282   if (!Trace_stream) return false;
283   vector<string> expected_lines = split(expected, "^D");
284   int curr_expected_line = 0;
285   while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
286     ++curr_expected_line;
287   if (curr_expected_line == SIZE(expected_lines)) return true;
288   string label, contents;
289   split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
290   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
291     if (label != p->label) continue;
292     if (contents != trim(p->contents)) continue;
293     ++curr_expected_line;
294     while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
295       ++curr_expected_line;
296     if (curr_expected_line == SIZE(expected_lines)) return true;
297     split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
298   }
299 
300   if (line_exists_anywhere(label, contents)) {
301     cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): line [" << label << ": " << contents << "] out of order in trace:\n";
302     DUMP("");
303   }
304   else {
305     cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): missing [" << contents << "] in trace:\n";
306     DUMP(label);
307   }
308   Passed = false;
309   return false;
310 }
311 
312 void split_label_contents(const string& s, string* label, string* contents) {
313   static const string delim(": ");
314   size_t pos = s.find(delim);
315   if (pos == string::npos) {
316     *label = "";
317     *contents = trim(s);
318   }
319   else {
320     *label = trim(s.substr(0, pos));
321     *contents = trim(s.substr(pos+SIZE(delim)));
322   }
323 }
324 
325 bool line_exists_anywhere(const string& label, const string& 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     if (contents == trim(p->contents)) return true;
329   }
330   return false;
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 bool trace_doesnt_contain(string label, string line) {
362   return trace_count(label, line) == 0;
363 }
364 
365 bool trace_doesnt_contain(string expected) {
366   vector<string> tmp = split_first(expected, ": ");
367   if (SIZE(tmp) == 1) {
368     raise << expected << ": missing label or contents in trace line\n" << end();
369     assert(false);
370   }
371   return trace_doesnt_contain(tmp.at(0), tmp.at(1));
372 }
373 
374 vector<string> split(string s, string delim) {
375   vector<string> result;
376   size_t begin=0, end=s.find(delim);
377   while (true) {
378     if (end == string::npos) {
379       result.push_back(string(s, begin, string::npos));
380       break;
381     }
382     result.push_back(string(s, begin, end-begin));
383     begin = end+SIZE(delim);
384     end = s.find(delim, begin);
385   }
386   return result;
387 }
388 
389 vector<string> split_first(string s, string delim) {
390   vector<string> result;
391   size_t end=s.find(delim);
392   result.push_back(string(s, 0, end));
393   if (end != string::npos)
394     result.push_back(string(s, end+SIZE(delim), string::npos));
395   return result;
396 }
397 
398 string trim(const string& s) {
399   string::const_iterator first = s.begin();
400   while (first != s.end() && isspace(*first))
401     ++first;
402   if (first == s.end()) return "";
403 
404   string::const_iterator last = --s.end();
405   while (last != s.begin() && isspace(*last))
406     --last;
407   ++last;
408   return string(first, last);
409 }
410 
411 :(before "End Includes")
412 #include <vector>
413 using std::vector;
414 #include <list>
415 using std::list;
416 #include <set>
417 using std::set;
418 
419 #include <sstream>
420 using std::istringstream;
421 using std::ostringstream;
422 
423 #include <fstream>
424 using std::ifstream;
425 using std::ofstream;