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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 *white-box*
//: testing. We focus on the domain of inputs the whole program needs to
//: handle rather than the correctness of individual functions. All white-box
//: 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 for these facts in the trace:
//: CHECK_TRACE_CONTENTS("label", "fact 1: 34\n"
//: "fact 2: 35\n");
//:
//: 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 focusing on 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 all
//: 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 tests
//: 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)
//:: == Core data structures
:(before "End Globals")
trace_stream* Trace_stream = NULL;
:(before "End Types")
struct trace_stream {
vector<trace_line> past_lines;
// End trace_stream Fields
trace_stream() {
// End trace_stream Constructor
}
~trace_stream() {
// End trace_stream Destructor
}
// End trace_stream Methods
};
//:: == Adding to the trace
//: Top-level method is trace() which can be used like an ostream. Usage:
//: trace(depth, label) << ... << end();
//: Don't forget the 'end()' to actually append to the trace.
:(before "End Includes")
// No brackets around the expansion so that it prints nothing if Trace_stream
// isn't initialized.
#define trace(...) !Trace_stream ? cerr : Trace_stream->stream(__VA_ARGS__)
:(before "End trace_stream Fields")
// accumulator for current trace_line
ostringstream* curr_stream;
string curr_label;
int curr_depth;
// other stuff
int collect_depth; // avoid tracing lower levels for speed
ofstream null_stream; // never opened, so writes to it silently fail
//: Some constants.
:(before "struct trace_stream") // include constants in all cleaved compilation units
const int Max_depth = 9999;
:(before "End trace_stream Constructor")
curr_stream = NULL;
curr_depth = Max_depth;
collect_depth = Max_depth;
:(before "struct trace_stream")
struct trace_line {
string contents;
string label;
int depth; // 0 is 'sea level'; positive integers are progressively 'deeper' and lower level
trace_line(string c, string l) {
contents = c;
label = l;
depth = 0;
}
trace_line(string c, string l, int d) {
contents = c;
label = l;
depth = d;
}
};
//: Starting a new trace line.
:(before "End trace_stream Methods")
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;
return *curr_stream;
}
//: End of a trace line; append it to the trace.
:(before "End Types")
struct end {};
:(code)
ostream& operator<<(ostream& os, end /*unused*/) {
if (Trace_stream) Trace_stream->newline();
return os;
}
:(before "End trace_stream Methods")
void newline();
:(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_contents, trim(curr_label), curr_depth)); // preserve indent in contents
// maybe incrementally dump trace
trace_line& t = past_lines.back();
if (should_incrementally_print_trace()) {
cerr << std::setw(4) << t.depth << ' ' << t.label << ": " << t.contents << '\n';
}
// End trace Commit
}
// clean up
delete curr_stream;
curr_stream = NULL;
curr_label.clear();
curr_depth = Max_depth;
}
//:: == Initializing the trace in tests
:(before "End Includes")
#define START_TRACING_UNTIL_END_OF_SCOPE lease_tracer leased_tracer;
:(before "End Test Setup")
START_TRACING_UNTIL_END_OF_SCOPE
//: 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() {
delete Trace_stream;
Trace_stream = NULL;
}
//:: == Errors using traces
:(before "End Includes")
#define raise (!Trace_stream ? (scroll_to_bottom_and_close_console(),++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Error_depth, "error"))
//: Print errors to the screen by default.
:(before "struct trace_stream") // include constants in all cleaved compilation units
const int Error_depth = 0;
:(before "End Globals")
int Hide_errors = false; // if set, don't print errors to screen
:(before "End Reset")
Hide_errors = false;
:(code)
bool trace_stream::should_incrementally_print_trace() {
if (!Hide_errors && curr_depth == Error_depth) return true;
// End Incremental Trace Print Conditions
return false;
}
:(before "End trace_stream Methods")
bool should_incrementally_print_trace();
:(before "End Globals")
int Trace_errors = 0; // used only when Trace_stream is NULL
// Fail tests that displayed (unexpected) errors.
// Expected errors 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 Includes")
// 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
//: Automatically close the console in some situations.
:(before "End One-time Setup")
atexit(scroll_to_bottom_and_close_console);
:(code)
void scroll_to_bottom_and_close_console() {
if (!tb_is_active()) return;
// leave the screen in a relatively clean state
tb_set_cursor(tb_width()-1, tb_height()-1);
cout << "\r\n";
tb_shutdown();
}
:(before "End Includes")
#include "termbox/termbox.h"
//:: == Other assertions on traces
//: Primitives:
//: - CHECK_TRACE_CONTENTS(lines)
//: Assert that the trace contains the given lines (separated by newlines)
//: in order. There can be other intervening lines between them.
//: - CHECK_TRACE_DOESNT_CONTAIN(line)
//: - CHECK_TRACE_DOESNT_CONTAIN(label, contents)
//: Assert that the trace doesn't contain the given (single) line.
//: - CHECK_TRACE_COUNT(label, count)
//: Assert that the trace contains exactly 'count' lines with the given
//: 'label'.
//: - CHECK_TRACE_CONTAINS_ERRORS()
//: - CHECK_TRACE_DOESNT_CONTAIN_ERRORS()
//: - trace_count_prefix(label, prefix)
//: Count the number of trace lines with the given 'label' that start with
//: the given 'prefix'.
:(before "End Includes")
#define CHECK_TRACE_CONTENTS(...) check_trace_contents(__FUNCTION__, __FILE__, __LINE__, __VA_ARGS__)
#define CHECK_TRACE_DOESNT_CONTAIN(...) CHECK(trace_doesnt_contain(__VA_ARGS__))
#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_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; \
}
// Allow tests to ignore trace lines generated during setup.
#define CLEAR_TRACE delete Trace_stream, Trace_stream = new trace_stream
:(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, "\n");
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;
}
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_count(tmp.at(0), tmp.at(1)) == 0;
}
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;
}
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;
}
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;
}
//:: == Helpers for debugging using traces
:(before "End Includes")
// To debug why a test is failing, dump its trace using '?'.
#define DUMP(label) if (Trace_stream) cerr << Trace_stream->readable_contents(label);
// To add temporary prints to the trace, use 'dbg'.
// `git log` should never show any calls to 'dbg'.
#define dbg trace(0, "a")
//: Dump the entire trace to file where it can be browsed offline.
//: Dump the trace as it happens; that way you get something even if the
//: program crashes.
:(before "End Globals")
ofstream Trace_file;
:(before "End Commandline Options(*arg)")
else if (is_equal(*arg, "--trace")) {
Trace_stream = new trace_stream;
cerr << "saving trace to 'last_run'\n";
Trace_file.open("last_run");
// Add a dummy line up top; otherwise the `browse_trace` tool currently has
// no way to expand any lines above an error.
Trace_file << " 0 dummy: start\n";
}
:(before "End trace Commit")
if (Trace_file) {
Trace_file << std::setw(4) << t.depth << ' ' << t.label << ": " << t.contents << '\n';
}
:(before "End One-time Setup")
atexit(cleanup_main);
:(code)
void cleanup_main() {
if (Trace_file) Trace_file.close();
// End cleanup_main
}
:(before "End trace_stream Methods")
string readable_contents(string label) {
string trim(const string& s); // prototype
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();
}
//: Print traces to the screen as they happen.
//: Particularly useful when juggling multiple trace streams, like when
//: debugging sandboxes.
:(before "End Globals")
bool Dump_trace = false;
:(before "End Commandline Options(*arg)")
else if (is_equal(*arg, "--dump")) {
Dump_trace = true;
}
:(before "End Incremental Trace Print Conditions")
if (Dump_trace) return true;
//: Miscellaneous helpers.
:(code)
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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