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 :(before "End Globals")
 80 bool Hide_errors = false;
 81 bool Dump_trace = false;
 82 string Dump_label = "";
 83 :(before "End Reset")
 84 Hide_errors = false;
 85 Dump_trace = false;
 86 Dump_label = "";
 87 
 88 :(before "End Types")
 89 // Pre-define some global constants that trace_stream needs to know about.
 90 // Since they're in the Types section, they'll be included in any cleaved
 91 // compilation units. So no extern linkage.
 92 const int Max_depth = 9999;
 93 const int Error_depth = 0;  // definitely always print errors
 94 
 95 struct trace_stream {
 96   vector<trace_line> past_lines;
 97   // accumulator for current line
 98   ostringstream* curr_stream;
 99   string curr_label;
100   int curr_depth;
101   int callstack_depth;
102   int collect_depth;
103   ofstream null_stream;  // never opens a file, so writes silently fail
104   trace_stream() :curr_stream(NULL), curr_depth(Max_depth), callstack_depth(0), collect_depth(Max_depth) {}
105   ~trace_stream() { if (curr_stream) delete curr_stream; }
106 
107   ostream& stream(string label) {
108     return stream(Max_depth, label);
109   }
110 
111   ostream& stream(int depth, string label) {
112     if (depth > collect_depth) return null_stream;
113     curr_stream = new ostringstream;
114     curr_label = label;
115     curr_depth = depth;
116     return *curr_stream;
117   }
118 
119   // be sure to call this before messing with curr_stream or curr_label
120   void newline();
121   // useful for debugging
122   string readable_contents(string label);  // empty label = show everything
123 };
124 
125 :(code)
126 void trace_stream::newline() {
127   if (!curr_stream) return;
128   string curr_contents = curr_stream->str();
129   if (!curr_contents.empty()) {
130     past_lines.push_back(trace_line(curr_depth, trim(curr_label), curr_contents));  // preserve indent in contents
131     if ((!Hide_errors && curr_label == "error")
132         || Dump_trace
133         || (!Dump_label.empty() && curr_label == Dump_label))
134       cerr << curr_label << ": " << curr_contents << '\n';
135   }
136   delete curr_stream;
137   curr_stream = NULL;
138   curr_label.clear();
139   curr_depth = Max_depth;
140 }
141 
142 string trace_stream::readable_contents(string label) {
143   ostringstream output;
144   label = trim(label);
145   for (vector<trace_line>::iterator p = past_lines.begin();  p != past_lines.end();  ++p)
146     if (label.empty() || label == p->label) {
147       output << std::setw(4) << p->depth << ' ' << p->label << ": " << p->contents << '\n';
148     }
149   return output.str();
150 }
151 
152 :(before "End Globals")
153 trace_stream* Trace_stream = NULL;
154 int Trace_errors = 0;  // used only when Trace_stream is NULL
155 
156 :(before "End Includes")
157 #define CLEAR_TRACE  delete Trace_stream, Trace_stream = new trace_stream;
158 
159 // Top-level helper. IMPORTANT: can't nest
160 #define trace(...)  !Trace_stream ? cerr /*print nothing*/ : Trace_stream->stream(__VA_ARGS__)
161 
162 // Just for debugging; 'git log' should never show any calls to 'dbg'.
163 #define dbg trace(0, "a")
164 #define DUMP(label)  if (Trace_stream) cerr << Trace_stream->readable_contents(label);
165 
166 // Errors are a special layer.
167 #define raise  (!Trace_stream ? (++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Error_depth, "error"))
168 // If we aren't yet sure how to deal with some corner case, use assert_for_now
169 // to indicate that it isn't an inviolable invariant.
170 #define assert_for_now assert
171 
172 // Inside tests, fail any tests that displayed (unexpected) errors.
173 // Expected errors in tests should always be hidden and silently checked for.
174 :(before "End Test Teardown")
175 if (Passed && !Hide_errors && trace_contains_errors()) {
176   Passed = false;
177 }
178 :(code)
179 bool trace_contains_errors() {
180   return Trace_errors > 0 || trace_count("error") > 0;
181 }
182 
183 :(before "End Types")
184 struct end {};
185 :(code)
186 ostream& operator<<(ostream& os, unused end) {
187   if (Trace_stream) Trace_stream->newline();
188   return os;
189 }
190 
191 :(before "End Globals")
192 bool Save_trace = false;
193 
194 // Trace_stream is a resource, lease_tracer uses RAII to manage it.
195 :(before "End Types")
196 struct lease_tracer {
197   lease_tracer();
198   ~lease_tracer();
199 };
200 :(code)
201 lease_tracer::lease_tracer() { Trace_stream = new trace_stream; }
202 lease_tracer::~lease_tracer() {
203   if (!Trace_stream) return;  // in case tests close Trace_stream
204   if (Save_trace) {
205     ofstream fout("last_trace");
206     fout << Trace_stream->readable_contents("");
207     fout.close();
208   }
209   delete Trace_stream, Trace_stream = NULL;
210 }
211 :(before "End Includes")
212 #define START_TRACING_UNTIL_END_OF_SCOPE  lease_tracer leased_tracer;
213 :(before "End Test Setup")
214 START_TRACING_UNTIL_END_OF_SCOPE
215 
216 :(before "End Includes")
217 #define CHECK_TRACE_CONTENTS(...)  check_trace_contents(__FUNCTION__, __FILE__, __LINE__, __VA_ARGS__)
218 
219 #define CHECK_TRACE_CONTAINS_ERRORS()  CHECK(trace_contains_errors())
220 #define CHECK_TRACE_DOESNT_CONTAIN_ERRORS() \
221   if (Passed && trace_contains_errors()) { \
222     cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): unexpected errors\n"; \
223     DUMP("error"); \
224     Passed = false; \
225     return; \
226   }
227 
228 #define CHECK_TRACE_COUNT(label, count) \
229   if (Passed && trace_count(label) != (count)) { \
230     cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): trace_count of " << label << " should be " << count << '\n'; \
231     cerr << "  got " << trace_count(label) << '\n';  /* multiple eval */ \
232     DUMP(label); \
233     Passed = false; \
234     return;  /* Currently we stop at the very first failure. */ \
235   }
236 
237 #define CHECK_TRACE_DOESNT_CONTAIN(...)  CHECK(trace_doesnt_contain(__VA_ARGS__))
238 
239 :(code)
240 bool check_trace_contents(string FUNCTION, string FILE, int LINE, string expected) {
241   if (!Passed) return false;
242   if (!Trace_stream) return false;
243   vector<string> expected_lines = split(expected, "^D");
244   int curr_expected_line = 0;
245   while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
246     ++curr_expected_line;
247   if (curr_expected_line == SIZE(expected_lines)) return true;
248   string label, contents;
249   split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
250   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
251     if (label != p->label) continue;
252     if (contents != trim(p->contents)) continue;
253     ++curr_expected_line;
254     while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
255       ++curr_expected_line;
256     if (curr_expected_line == SIZE(expected_lines)) return true;
257     split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
258   }
259 
260   if (line_exists_anywhere(label, contents)) {
261     cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): line [" << label << ": " << contents << "] out of order in trace:\n";
262     DUMP("");
263   }
264   else {
265     cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): missing [" << contents << "] in trace:\n";
266     DUMP(label);
267   }
268   Passed = false;
269   return false;
270 }
271 
272 void split_label_contents(const string& s, string* label, string* contents) {
273   static const string delim(": ");
274   size_t pos = s.find(delim);
275   if (pos == string::npos) {
276     *label = "";
277     *contents = trim(s);
278   }
279   else {
280     *label = trim(s.substr(0, pos));
281     *contents = trim(s.substr(pos+SIZE(delim)));
282   }
283 }
284 
285 bool line_exists_anywhere(const string& label, const string& contents) {
286   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
287     if (label != p->label) continue;
288     if (contents == trim(p->contents)) return true;
289   }
290   return false;
291 }
292 
293 int trace_count(string label) {
294   return trace_count(label, "");
295 }
296 
297 int trace_count(string label, string line) {
298   if (!Trace_stream) return 0;
299   long result = 0;
300   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
301     if (label == p->label) {
302       if (line == "" || trim(line) == trim(p->contents))
303         ++result;
304     }
305   }
306   return result;
307 }
308 
309 int trace_count_prefix(string label, string prefix) {
310   if (!Trace_stream) return 0;
311   long result = 0;
312   for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin();  p != Trace_stream->past_lines.end();  ++p) {
313     if (label == p->label) {
314       if (starts_with(trim(p->contents), trim(prefix)))
315         ++result;
316     }
317   }
318   return result;
319 }
320 
321 bool trace_doesnt_contain(string label, string line) {
322   return trace_count(label, line) == 0;
323 }
324 
325 bool trace_doesnt_contain(string expected) {
326   vector<string> tmp = split_first(expected, ": ");
327   return trace_doesnt_contain(tmp.at(0), tmp.at(1));
328 }
329 
330 vector<string> split(string s, string delim) {
331   vector<string> result;
332   size_t begin=0, end=s.find(delim);
333   while (true) {
334     if (end == string::npos) {
335       result.push_back(string(s, begin, string::npos));
336       break;
337     }
338     result.push_back(string(s, begin, end-begin));
339     begin = end+SIZE(delim);
340     end = s.find(delim, begin);
341   }
342   return result;
343 }
344 
345 vector<string> split_first(string s, string delim) {
346   vector<string> result;
347   size_t end=s.find(delim);
348   result.push_back(string(s, 0, end));
349   if (end != string::npos)
350     result.push_back(string(s, end+SIZE(delim), string::npos));
351   return result;
352 }
353 
354 string trim(const string& s) {
355   string::const_iterator first = s.begin();
356   while (first != s.end() && isspace(*first))
357     ++first;
358   if (first == s.end()) return "";
359 
360   string::const_iterator last = --s.end();
361   while (last != s.begin() && isspace(*last))
362     --last;
363   ++last;
364   return string(first, last);
365 }
366 
367 :(before "End Includes")
368 #include <vector>
369 using std::vector;
370 #include <list>
371 using std::list;
372 #include <map>
373 using std::map;
374 #include <set>
375 using std::set;
376 #include <algorithm>
377 
378 #include <sstream>
379 using std::istringstream;
380 using std::ostringstream;
381 
382 #include <fstream>
383 using std::ifstream;
384 using std::ofstream;
385 
386 :(before "End Globals")
387 //: In future layers we'll use the depth field as follows:
388 //:
389 //: Errors will be depth 0.
390 //: Mu 'applications' will be able to use depths 1-100 as they like.
391 //: Primitive statements will occupy 101-9989
392 extern const int Initial_callstack_depth = 101;
393 extern const int Max_callstack_depth = 9989;
394 //: Finally, details of primitive Mu statements will occupy depth 9990-9999
395 //: (more on that later as well)
396 //:
397 //: This framework should help us hide some details at each level, mixing
398 //: static ideas like layers with the dynamic notion of call-stack depth.