902: c++: calling recipes with ingredients - mu - Soul of a tiny new machine. More thorough tests → More comprehensible and rewrite-friendly software → More resilient society.

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author	Kartik K. Agaram <vc@akkartik.com>	2015-03-14 00:07:44 -0700
committer	Kartik K. Agaram <vc@akkartik.com>	2015-03-14 00:09:47 -0700
commit	df8bb4c30d8ef534ddde50a4ac8ce9ecb411b72f (patch)
tree	1c85150627cff86ded3568a62a1f1a1cbed363c4 /cpp/.traces/calling_recipe
parent	f7051fadd90af17820df750d448dc35ea63690e3 (diff)
download	mu-df8bb4c30d8ef534ddde50a4ac8ce9ecb411b72f.tar.gz

902: c++: calling recipes with ingredients

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cpp/.traces/calling_recipe

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//: The goal of layers is to make programs more easy to understand and more //: malleable, easy to rewrite in radical ways without accidentally breaking //: some corner case. Tests further both goals. They help understandability by //: letting one make small changes and get feedback. What if I wrote this line //: like so? What if I removed this function call, is it really necessary? //: Just try it, see if the tests pass. Want to explore rewriting this bit in //: this way? Tests put many refactorings on a firmer footing. //: //: But the usual way we write tests seems incomplete. Refactorings tend to //: work in the small, but don't help with changes to function boundaries. If //: you want to extract a new function you have to manually test-drive it to //: create tests for it. If you want to inline a function its tests are no //: longer valid. In both cases you end up having to reorganize code as well as //: tests, an error-prone activity. //: //: In response, this layer introduces the notion of *domain-driven* testing. //: We focus on the domain of inputs the whole program needs to handle rather //: than the correctness of individual functions. All tests invoke the program //: in a single way: by calling run() with some input. As the program operates //: on the input, it traces out a list of _facts_ deduced about the domain: //: trace("label") << "fact 1: " << val; //: //: Tests can now check these facts: //: :(scenario foo) //: 34 # call run() with this input //: +label: fact 1: 34 # 'run' should have deduced this fact //: -label: fact 1: 35 # the trace should not contain such a fact //: //: Since we never call anything but the run() function directly, we never have //: to rewrite the tests when we reorganize the internals of the program. We //: just have to make sure our rewrite deduces the same facts about the domain, //: and that's something we're going to have to do anyway. //: //: To avoid the combinatorial explosion of integration tests, each layer //: mainly logs facts to the trace with a common *label*. All tests in a layer //: tend to check facts with this label. Validating the facts logged with a //: specific label is like calling functions of that layer directly. //: //: To build robust tests, trace facts about your domain rather than details of //: how you computed them. //: //: More details: http://akkartik.name/blog/tracing-tests //: //: --- //: //: Between layers and domain-driven testing, programming starts to look like a //: fundamentally different activity. Instead of a) superficial, b) local rules //: on c) code [like say http://blog.bbv.ch/2013/06/05/clean-code-cheat-sheet], //: we allow programmers to engage with the a) deep, b) global structure of the //: c) domain. If you can systematically track discontinuities in the domain, //: you don't care if the code used gotos as long as it passed the tests. If //: tests become more robust to run it becomes easier to try out radically //: different implementations for the same program. If code is super-easy to //: rewrite, it becomes less important what indentation style it uses, or that //: the objects are appropriately encapsulated, or that the functions are //: referentially transparent. //: //: Instead of plumbing, programming becomes building and gradually refining a //: map of the environment the program must operate under. Whether a program is //: 'correct' at a given point in time is a red herring; what matters is //: avoiding regression by monotonically nailing down the more 'eventful' parts //: of the terrain. It helps readers new and old, and rewards curiosity, to //: organize large programs in self-similar hierarchies of example scenarios //: colocated with the code that makes them work. //: //: "Programming properly should be regarded as an activity by which //: programmers form a mental model, rather than as production of a program." //: -- Peter Naur (http://alistair.cockburn.us/ASD+book+extract%3A+%22Naur,+Ehn,+Musashi%22) :(before "End Types") struct trace_line { int depth; // optional field just to help browse traces later string label; string contents; trace_line(string l, string c) :depth(0), label(l), contents(c) {} trace_line(int d, string l, string c) :depth(d), label(l), contents(c) {} }; //: Support for tracing an entire run. //: Traces can have a lot of overhead, so only turn them on when asked. :(before "End Commandline Options(*arg)") else if (is_equal(*arg, "--trace")) { Save_trace = true; } :(before "End Commandline Parsing") if (Save_trace) { cerr << "initializing trace\n"; Trace_stream = new trace_stream; } :(code) void cleanup_main() { if (!Trace_stream) return; if (Save_trace) Trace_stream->save(); delete Trace_stream; Trace_stream = NULL; } :(before "End One-time Setup") atexit(cleanup_main); :(before "End Types") // Pre-define some global constants that trace_stream needs to know about. // Since they're in the Types section, they'll be included in any cleaved // compilation units. So no extern linkage. const int Max_depth = 9999; const int Error_depth = 0; // definitely always print errors const int Warn_depth = 1; struct trace_stream { vector<trace_line> past_lines; // accumulator for current line ostringstream* curr_stream; string curr_label; int curr_depth; int collect_depth; ofstream null_stream; // never opens a file, so writes silently fail trace_stream() :curr_stream(NULL), curr_depth(Max_depth), collect_depth(Max_depth) {} ~trace_stream() { if (curr_stream) delete curr_stream; } ostream& stream(string label) { return stream(Max_depth, label); } ostream& stream(int depth, string label) { if (depth > collect_depth) return null_stream; curr_stream = new ostringstream; curr_label = label; curr_depth = depth; (*curr_stream) << std::hex; return *curr_stream; } void save() { cerr << "saving trace to 'last_run'\n"; ofstream fout("last_run"); fout << readable_contents(""); fout.close(); } // be sure to call this before messing with curr_stream or curr_label void newline(); // useful for debugging string readable_contents(string label); // empty label = show everything }; :(code) void trace_stream::newline() { if (!curr_stream) return; string curr_contents = curr_stream->str(); if (!curr_contents.empty()) { past_lines.push_back(trace_line(curr_depth, trim(curr_label), curr_contents)); // preserve indent in contents if ((!Hide_errors && curr_depth == Error_depth) || (!Hide_warnings && !Hide_errors && curr_depth == Warn_depth) || Dump_trace || (!Dump_label.empty() && curr_label == Dump_label)) cerr << curr_label << ": " << curr_contents << '\n'; } delete curr_stream; curr_stream = NULL; curr_label.clear(); curr_depth = Max_depth; } string trace_stream::readable_contents(string label) { ostringstream output; label = trim(label); for (vector<trace_line>::iterator p = past_lines.begin(); p != past_lines.end(); ++p) if (label.empty() || label == p->label) { output << std::setw(4) << p->depth << ' ' << p->label << ": " << p->contents << '\n'; } return output.str(); } :(before "End Globals") trace_stream* Trace_stream = NULL; int Trace_errors = 0; // used only when Trace_stream is NULL :(before "End Globals") bool Hide_errors = false; // if set, don't print even error trace lines to screen bool Hide_warnings = false; // if set, don't print warnings to screen bool Dump_trace = false; // if set, print trace lines to screen string Dump_label = ""; // if set, print trace lines matching a single label to screen :(before "End Reset") Hide_errors = false; Hide_warnings = false; Dump_trace = false; Dump_label = ""; //: Never dump warnings in scenarios :(before "End Test Setup") Hide_warnings = true; :(before "End Includes") #define CLEAR_TRACE delete Trace_stream, Trace_stream = new trace_stream; // Top-level helper. IMPORTANT: can't nest #define trace(...) !Trace_stream ? cerr /*print nothing*/ : Trace_stream->stream(__VA_ARGS__) // Just for debugging; 'git log' should never show any calls to 'dbg'. #define dbg trace(0, "a") #define DUMP(label) if (Trace_stream) cerr << Trace_stream->readable_contents(label); // Errors and warnings are special layers. #define raise (!Trace_stream ? (++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Error_depth, "error")) #define warn (!Trace_stream ? (++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Warn_depth, "warn")) // If we aren't yet sure how to deal with some corner case, use assert_for_now // to indicate that it isn't an inviolable invariant. #define assert_for_now assert #define raise_for_now raise // Inside tests, fail any tests that displayed (unexpected) errors. // Expected errors in tests should always be hidden and silently checked for. :(before "End Test Teardown") if (Passed && !Hide_errors && trace_contains_errors()) { Passed = false; } :(code) bool trace_contains_errors() { return Trace_errors > 0 || trace_count("error") > 0; } :(before "End Types") struct end {}; :(code) ostream& operator<<(ostream& os, end /*unused*/) { if (Trace_stream) Trace_stream->newline(); return os; } :(before "End Globals") bool Save_trace = false; // if set, write out trace to disk // Trace_stream is a resource, lease_tracer uses RAII to manage it. :(before "End Types") struct lease_tracer { lease_tracer(); ~lease_tracer(); }; :(code) lease_tracer::lease_tracer() { Trace_stream = new trace_stream; } lease_tracer::~lease_tracer() { if (Save_trace) Trace_stream->save(); delete Trace_stream, Trace_stream = NULL; } :(before "End Includes") #define START_TRACING_UNTIL_END_OF_SCOPE lease_tracer leased_tracer; :(before "End Test Setup") START_TRACING_UNTIL_END_OF_SCOPE :(before "End Includes") #define CHECK_TRACE_CONTENTS(...) check_trace_contents(__FUNCTION__, __FILE__, __LINE__, __VA_ARGS__) #define CHECK_TRACE_CONTAINS_ERRORS() CHECK(trace_contains_errors()) #define CHECK_TRACE_DOESNT_CONTAIN_ERRORS() \ if (Passed && trace_contains_errors()) { \ cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): unexpected errors\n"; \ DUMP("error"); \ Passed = false; \ return; \ } #define CHECK_TRACE_COUNT(label, count) \ if (Passed && trace_count(label) != (count)) { \ cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): trace_count of " << label << " should be " << count << '\n'; \ cerr << " got " << trace_count(label) << '\n'; /* multiple eval */ \ DUMP(label); \ Passed = false; \ return; /* Currently we stop at the very first failure. */ \ } #define CHECK_TRACE_DOESNT_CONTAIN(...) CHECK(trace_doesnt_contain(__VA_ARGS__)) :(code) bool check_trace_contents(string FUNCTION, string FILE, int LINE, string expected) { if (!Passed) return false; if (!Trace_stream) return false; vector<string> expected_lines = split(expected, ""); int curr_expected_line = 0; while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty()) ++curr_expected_line; if (curr_expected_line == SIZE(expected_lines)) return true; string label, contents; split_label_contents(expected_lines.at(curr_expected_line), &label, &contents); for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin(); p != Trace_stream->past_lines.end(); ++p) { if (label != p->label) continue; if (contents != trim(p->contents)) continue; ++curr_expected_line; while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty()) ++curr_expected_line; if (curr_expected_line == SIZE(expected_lines)) return true; split_label_contents(expected_lines.at(curr_expected_line), &label, &contents); } if (line_exists_anywhere(label, contents)) { cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): line [" << label << ": " << contents << "] out of order in trace:\n"; DUMP(""); } else { cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): missing [" << contents << "] in trace:\n"; DUMP(label); } Passed = false; return false; } void split_label_contents(const string& s, string* label, string* contents) { static const string delim(": "); size_t pos = s.find(delim); if (pos == string::npos) { *label = ""; *contents = trim(s); } else { *label = trim(s.substr(0, pos)); *contents = trim(s.substr(pos+SIZE(delim))); } } bool line_exists_anywhere(const string& label, const string& contents) { for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin(); p != Trace_stream->past_lines.end(); ++p) { if (label != p->label) continue; if (contents == trim(p->contents)) return true; } return false; } int trace_count(string label) { return trace_count(label, ""); } int trace_count(string label, string line) { if (!Trace_stream) return 0; long result = 0; for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin(); p != Trace_stream->past_lines.end(); ++p) { if (label == p->label) { if (line == "" || trim(line) == trim(p->contents)) ++result; } } return result; } int trace_count_prefix(string label, string prefix) { if (!Trace_stream) return 0; long result = 0; for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin(); p != Trace_stream->past_lines.end(); ++p) { if (label == p->label) { if (starts_with(trim(p->contents), trim(prefix))) ++result; } } return result; } bool trace_doesnt_contain(string label, string line) { return trace_count(label, line) == 0; } bool trace_doesnt_contain(string expected) { vector<string> tmp = split_first(expected, ": "); if (SIZE(tmp) == 1) { raise << expected << ": missing label or contents in trace line\n" << end(); assert(false); } return trace_doesnt_contain(tmp.at(0), tmp.at(1)); } vector<string> split(string s, string delim) { vector<string> result; size_t begin=0, end=s.find(delim); while (true) { if (end == string::npos) { result.push_back(string(s, begin, string::npos)); break; } result.push_back(string(s, begin, end-begin)); begin = end+SIZE(delim); end = s.find(delim, begin); } return result; } vector<string> split_first(string s, string delim) { vector<string> result; size_t end=s.find(delim); result.push_back(string(s, 0, end)); if (end != string::npos) result.push_back(string(s, end+SIZE(delim), string::npos)); return result; } string trim(const string& s) { string::const_iterator first = s.begin(); while (first != s.end() && isspace(*first)) ++first; if (first == s.end()) return ""; string::const_iterator last = --s.end(); while (last != s.begin() && isspace(*last)) --last; ++last; return string(first, last); } :(before "End Includes") #include <vector> using std::vector; #include <list> using std::list; #include <set> using std::set; #include <sstream> using std::istringstream; using std::ostringstream; #include <fstream> using std::ifstream; using std::ofstream;


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