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