Added coverage.py, and optional coverage info to test.py

Now coverage information can be collected if you provide the --coverage
to test.py. Internally this uses GCC's gcov instrumentation along with a
new script, coverage.py, to parse *.gcov files.

The main use for this is finding coverage info during CI runs. There's a
risk that the instrumentation may make it more difficult to debug, so I
decided to not make coverage collection enabled by default.

.github/workflows/test.yml

@@ -4,6 +4,7 @@ on: [push, pull_request]
 env:
   CFLAGS: -Werror
   MAKEFLAGS: -j
+  COVERAGE: 1
 
 jobs:
   # run tests
@@ -70,9 +71,10 @@ jobs:
             -Duser_provided_block_device_erase=NULL \
             -Duser_provided_block_device_sync=NULL \
             -include stdio.h"
-#      # normal+reentrant tests
+      # normal+reentrant tests
-#      - name: test-default
+      - name: test-default
-#        run: make test SCRIPTFLAGS+="-nrk"
+        continue-on-error: true
+        run: make test SCRIPTFLAGS+="-nrk"
 #      # NOR flash: read/prog = 1 block = 4KiB
 #      - name: test-nor
 #        run: make test SCRIPTFLAGS+="-nrk
@@ -102,6 +104,29 @@ jobs:
 #        run: make test SCRIPTFLAGS+="-nrk
 #          -DLFS_READ_SIZE=11 -DLFS_BLOCK_SIZE=704"
 
+      - name: test-default-what
+        run: |
+            echo "version"
+            gcov --version
+            echo "tests"
+            ls tests
+            echo "hmm"
+            cat tests/*.gcov
+            echo "woah"
+
+      # collect coverage
+      - name: collect-coverage
+        continue-on-error: true
+        run: |
+          mkdir -p coverage
+          mv results/coverage.gcov coverage/${{github.job}}.gcov
+      - name: upload-coverage
+        continue-on-error: true
+        uses: actions/upload-artifact@v2
+        with:
+          name: coverage
+          path: coverage
+
       # update results
       - uses: actions/checkout@v2
         if: github.ref != 'refs/heads/master'

Makefile

@@ -7,6 +7,7 @@ CC ?= gcc
 AR ?= ar
 SIZE ?= size
 NM ?= nm
+GCOV ?= gcov
 
 SRC += $(wildcard *.c bd/*.c)
 OBJ := $(SRC:.c=.o)
@@ -31,6 +32,12 @@ override CFLAGS += -Wextra -Wshadow -Wjump-misses-init -Wundef
 ifdef VERBOSE
 override SCRIPTFLAGS += -v
 endif
+ifdef EXEC
+override TESTFLAGS += $(patsubst %,--exec=%,$(EXEC))
+endif
+ifdef COVERAGE
+override TESTFLAGS += --coverage
+endif
 
 
 all: $(TARGET)
@@ -43,11 +50,14 @@ size: $(OBJ)
 code:
 	./scripts/code.py $(SCRIPTFLAGS)
 
+coverage:
+	./scripts/coverage.py $(SCRIPTFLAGS)
+
 test:
-	./scripts/test.py $(EXEC:%=--exec=%) $(SCRIPTFLAGS)
+	./scripts/test.py $(TESTFLAGS) $(SCRIPTFLAGS)
 .SECONDEXPANSION:
 test%: tests/test$$(firstword $$(subst \#, ,%)).toml
-	./scripts/test.py $@ $(EXEC:%=--exec=%) $(SCRIPTFLAGS)
+	./scripts/test.py $@ $(TESTFLAGS) $(SCRIPTFLAGS)
 
 -include $(DEP)
 
@@ -63,6 +73,9 @@ lfs: $(OBJ)
 %.s: %.c
 	$(CC) -S $(CFLAGS) $< -o $@
 
+%.gcda.gcov: %.gcda
+	( cd $(dir $@) ; $(GCOV) -ri $(notdir $<) )
+
 clean:
 	rm -f $(TARGET)
 	rm -f $(OBJ)
@@ -70,3 +83,4 @@ clean:
 	rm -f $(ASM)
 	rm -f tests/*.toml.*
 	rm -f sizes/*
+	rm -f results/*

scripts/coverage.py

@@ -0,0 +1,413 @@
+#!/usr/bin/env python3
+#
+
+import os
+import glob
+import csv
+import re
+import collections as co
+import bisect as b
+
+RESULTDIR = 'results'
+#RULES = """
+#define FLATTEN
+#%(sizedir)s/%(build)s.$(subst /,.,$(target)): $(target)
+#    ( echo "#line 1 \\"$$<\\"" ; %(cat)s $$< ) > $$@
+#%(sizedir)s/%(build)s.$(subst /,.,$(target:.c=.size)): \\
+#        %(sizedir)s/%(build)s.$(subst /,.,$(target:.c=.o))
+#    $(NM) --size-sort $$^ | sed 's/^/$(subst /,\\/,$(target:.c=.o)):/' > $$@
+#endef
+#$(foreach target,$(SRC),$(eval $(FLATTEN)))
+#
+#-include %(sizedir)s/*.d
+#.SECONDARY:
+#
+#%%.size: $(foreach t,$(subst /,.,$(OBJ:.o=.size)),%%.$t)
+#    cat $^ > $@
+#"""
+#CATS = {
+#    'code': 'cat',
+#    'code_inlined': 'sed \'s/^static\( inline\)\?//\'',
+#}
+#
+#def build(**args):
+#    # mkdir -p sizedir
+#    os.makedirs(args['sizedir'], exist_ok=True)
+#
+#    if args.get('inlined', False):
+#        builds = ['code', 'code_inlined']
+#    else:
+#        builds = ['code']
+#
+#    # write makefiles for the different types of builds
+#    makefiles = []
+#    targets = []
+#    for build in builds:
+#        path = args['sizedir'] + '/' + build
+#        with open(path + '.mk', 'w') as mk:
+#            mk.write(RULES.replace(4*' ', '\t') % dict(
+#                sizedir=args['sizedir'],
+#                build=build,
+#                cat=CATS[build]))
+#            mk.write('\n')
+#
+#            # pass on defines
+#            for d in args['D']:
+#                mk.write('%s: override CFLAGS += -D%s\n' % (
+#                    path+'.size', d))
+#
+#        makefiles.append(path + '.mk')
+#        targets.append(path + '.size')
+#
+#    # build in parallel
+#    cmd = (['make', '-f', 'Makefile'] +
+#        list(it.chain.from_iterable(['-f', m] for m in makefiles)) +
+#        [target for target in targets])
+#    if args.get('verbose', False):
+#        print(' '.join(shlex.quote(c) for c in cmd))
+#    proc = sp.Popen(cmd,
+#        stdout=sp.DEVNULL if not args.get('verbose', False) else None)
+#    proc.wait()
+#    if proc.returncode != 0:
+#        sys.exit(-1)
+#
+#    # find results
+#    build_results = co.defaultdict(lambda: 0)
+#    # notes
+#    # - filters type
+#    # - discards internal/debug functions (leading __)
+#    pattern = re.compile(
+#        '^(?P<file>[^:]+)' +
+#        ':(?P<size>[0-9a-fA-F]+)' +
+#        ' (?P<type>[%s])' % re.escape(args['type']) +
+#        ' (?!__)(?P<name>.+?)$')
+#    for build in builds:
+#        path = args['sizedir'] + '/' + build
+#        with open(path + '.size') as size:
+#            for line in size:
+#                match = pattern.match(line)
+#                if match:
+#                    file = match.group('file')
+#                    # discard .8449 suffixes created by optimizer
+#                    name = re.sub('\.[0-9]+', '', match.group('name'))
+#                    size = int(match.group('size'), 16)
+#                    build_results[(build, file, name)] += size
+#
+#    results = []
+#    for (build, file, name), size in build_results.items():
+#        if build == 'code':
+#            results.append((file, name, size, False))
+#        elif (build == 'code_inlined' and
+#                ('inlined', file, name) not in results):
+#            results.append((file, name, size, True))
+#
+#    return results
+
+def collect(covfuncs, covlines, path, **args):
+    with open(path) as f:
+        file = None
+        filter = args['filter'].split() if args.get('filter') else None
+        pattern = re.compile(
+            '^(?P<file>file'
+                ':(?P<file_name>.*))' +
+            '|(?P<func>function' +
+                ':(?P<func_lineno>[0-9]+)' +
+                ',(?P<func_hits>[0-9]+)' +
+                ',(?P<func_name>.*))' +
+            '|(?P<line>lcount' +
+                ':(?P<line_lineno>[0-9]+)' +
+                ',(?P<line_hits>[0-9]+))$')
+        for line in f:
+            match = pattern.match(line)
+            if match:
+                if match.group('file'):
+                    file = match.group('file_name')
+                    # filter?
+                    if filter and file not in filter:
+                        file = None
+                elif file is not None and match.group('func'):
+                    lineno = int(match.group('func_lineno'))
+                    name, hits = covfuncs[(file, lineno)]
+                    covfuncs[(file, lineno)] = (
+                        name or match.group('func_name'),
+                        hits + int(match.group('func_hits')))
+                elif file is not None and match.group('line'):
+                    lineno = int(match.group('line_lineno'))
+                    covlines[(file, lineno)] += int(match.group('line_hits'))
+
+def coverage(**args):
+    # find *.gcov files
+    gcovpaths = []
+    for gcovpath in args.get('gcovpaths') or [args['results']]:
+        if os.path.isdir(gcovpath):
+            gcovpath = gcovpath + '/*.gcov'
+
+        for path in glob.glob(gcovpath):
+            gcovpaths.append(path)
+
+    if not gcovpaths:
+        print('no gcov files found in %r?'
+            % (args.get('gcovpaths') or [args['results']]))
+        sys.exit(-1)
+
+    # collect coverage info
+    covfuncs = co.defaultdict(lambda: (None, 0))
+    covlines = co.defaultdict(lambda: 0)
+    for path in gcovpaths:
+        collect(covfuncs, covlines, path, **args)
+
+    # merge? go ahead and handle that here, but
+    # with a copy so we only report on the current coverage
+    if args.get('merge', None):
+        if os.path.isfile(args['merge']):
+            accfuncs = covfuncs.copy()
+            acclines = covlines.copy()
+            collect(accfuncs, acclines, args['merge']) # don't filter!
+        else:
+            accfuncs = covfuncs
+            acclines = covlines
+
+        accfiles = sorted({file for file, _ in acclines.keys()})
+        accfuncs, i = sorted(accfuncs.items()), 0 
+        acclines, j = sorted(acclines.items()), 0
+        with open(args['merge'], 'w') as f:
+            for file in accfiles:
+                f.write('file:%s\n' % file)
+                while i < len(accfuncs) and accfuncs[i][0][0] == file:
+                    ((_, lineno), (name, hits)) = accfuncs[i]
+                    f.write('function:%d,%d,%s\n' % (lineno, hits, name))
+                    i += 1
+                while j < len(acclines) and acclines[j][0][0] == file:
+                    ((_, lineno), hits) = acclines[j]
+                    f.write('lcount:%d,%d\n' % (lineno, hits))
+                    j += 1
+
+    # annotate?
+    if args.get('annotate', False):
+        # annotate(covlines, **args)
+        pass
+
+    # condense down to file/function results
+    funcs = sorted(covfuncs.items())
+    func_lines = [(file, lineno) for (file, lineno), _ in funcs]
+    func_names = [name for _, (name, _) in funcs]
+    def line_func(file, lineno):
+        i = b.bisect(func_lines, (file, lineno))
+        if i and func_lines[i-1][0] == file:
+            return func_names[i-1]
+        else:
+            return '???'
+
+    func_results = co.defaultdict(lambda: (0, 0))
+    for ((file, lineno), hits) in covlines.items():
+        func = line_func(file, lineno)
+        branch_hits, branches = func_results[(file, func)]
+        func_results[(file, func)] = (branch_hits + (hits > 0), branches + 1)
+
+    results = []
+    for (file, func), (hits, branches) in func_results.items():
+        # discard internal/testing functions (test_* injected with
+        # internal testing)
+        if func == '???' or func.startswith('__') or func.startswith('test_'):
+            continue
+        # discard .8449 suffixes created by optimizer
+        func = re.sub('\.[0-9]+', '', func)
+        results.append((file, func, hits, branches))
+
+    return results
+
+
+def main(**args):
+    # find coverage
+    if not args.get('input', None):
+        results = coverage(**args)
+    else:
+        with open(args['input']) as f:
+            r = csv.DictReader(f)
+            results = [
+                (   result['file'],
+                    result['function'],
+                    int(result['hits']),
+                    int(result['branches']))
+                for result in r]
+
+    total_hits, total_branches = 0, 0
+    for _, _, hits, branches in results:
+        total_hits += hits
+        total_branches += branches
+
+    # find previous results?
+    if args.get('diff', None):
+        with open(args['diff']) as f:
+            r = csv.DictReader(f)
+            prev_results = [
+                (   result['file'],
+                    result['function'],
+                    int(result['hits']),
+                    int(result['branches']))
+                for result in r]
+
+        prev_total_hits, prev_total_branches = 0, 0
+        for _, _, hits, branches in prev_results:
+            prev_total_hits += hits
+            prev_total_branches += branches
+
+    # write results to CSV
+    if args.get('output', None):
+        results.sort(key=lambda x: (-(x[2]/x[3]), -x[3], x))
+        with open(args['output'], 'w') as f:
+            w = csv.writer(f)
+            w.writerow(['file', 'function', 'hits', 'branches'])
+            for file, func, hits, branches in results:
+                w.writerow((file, func, hits, branches))
+
+    # print results
+    def dedup_entries(results, by='function'):
+        entries = co.defaultdict(lambda: (0, 0))
+        for file, func, hits, branches in results:
+            entry = (file if by == 'file' else func)
+            entry_hits, entry_branches = entries[entry]
+            entries[entry] = (entry_hits + hits, entry_branches + branches)
+        return entries
+
+    def diff_entries(olds, news):
+        diff = co.defaultdict(lambda: (None, None, None, None, None, None))
+        for name, (new_hits, new_branches) in news.items():
+            diff[name] = (
+                0, 0,
+                new_hits, new_branches,
+                new_hits, new_branches)
+        for name, (old_hits, old_branches) in olds.items():
+            new_hits = diff[name][2] or 0
+            new_branches = diff[name][3] or 0
+            diff[name] = (
+                old_hits, old_branches,
+                new_hits, new_branches,
+                new_hits-old_hits, new_branches-old_branches)
+        return diff
+
+    def print_header(by=''):
+        if not args.get('diff', False):
+            print('%-36s %11s' % (by, 'branches'))
+        else:
+            print('%-36s %11s %11s %11s' % (by, 'old', 'new', 'diff'))
+
+    def print_entries(by='function'):
+        entries = dedup_entries(results, by=by)
+
+        if not args.get('diff', None):
+            print_header(by=by)
+            for name, (hits, branches) in sorted(entries.items(),
+                    key=lambda x: (-(x[1][0]-x[1][1]), -x[1][1], x)):
+                print("%-36s %11s (%.2f%%)" % (name,
+                    '%d/%d' % (hits, branches),
+                    100*(hits/branches if branches else 1.0)))
+        else:
+            prev_entries = dedup_entries(prev_results, by=by)
+            diff = diff_entries(prev_entries, entries)
+            print_header(by='%s (%d added, %d removed)' % (by,
+                sum(1 for _, old, _, _, _, _ in diff.values() if not old),
+                sum(1 for _, _, _, new, _, _ in diff.values() if not new)))
+            for name, (
+                    old_hits, old_branches,
+                    new_hits, new_branches,
+                    diff_hits, diff_branches) in sorted(diff.items(),
+                        key=lambda x: (
+                            -(x[1][4]-x[1][5]), -x[1][5], -x[1][3], x)):
+                ratio = ((new_hits/new_branches if new_branches else 1.0)
+                    - (old_hits/old_branches if old_branches else 1.0))
+                if diff_hits or diff_branches or args.get('all', False):
+                    print("%-36s %11s %11s %11s%s" % (name,
+                        '%d/%d' % (old_hits, old_branches)
+                            if old_branches else '-',
+                        '%d/%d' % (new_hits, new_branches)
+                            if new_branches else '-',
+                        '%+d/%+d' % (diff_hits, diff_branches),
+                        ' (%+.2f%%)' % (100*ratio) if ratio else ''))
+
+    def print_totals():
+        if not args.get('diff', None):
+            print("%-36s %11s (%.2f%%)" % ('TOTALS',
+                '%d/%d' % (total_hits, total_branches),
+                100*(total_hits/total_branches if total_branches else 1.0)))
+        else:
+            ratio = ((total_hits/total_branches
+                    if total_branches else 1.0)
+                - (prev_total_hits/prev_total_branches
+                    if prev_total_branches else 1.0))
+            print("%-36s %11s %11s %11s%s" % ('TOTALS',
+                '%d/%d' % (prev_total_hits, prev_total_branches),
+                '%d/%d' % (total_hits, total_branches),
+                '%+d/%+d' % (total_hits-prev_total_hits,
+                    total_branches-prev_total_branches),
+                ' (%+.2f%%)' % (100*ratio) if ratio else ''))
+
+    def print_status():
+        if not args.get('diff', None):
+            print("%d/%d (%.2f%%)" % (total_hits, total_branches,
+                100*(total_hits/total_branches if total_branches else 1.0)))
+        else:
+            ratio = ((total_hits/total_branches
+                    if total_branches else 1.0)
+                - (prev_total_hits/prev_total_branches
+                    if prev_total_branches else 1.0))
+            print("%d/%d (%+.2f%%)" % (total_hits, total_branches,
+                (100*ratio) if ratio else ''))
+
+    if args.get('quiet', False):
+        pass
+    elif args.get('status', False):
+        print_status()
+    elif args.get('summary', False):
+        print_header()
+        print_totals()
+    elif args.get('files', False):
+        print_entries(by='file')
+        print_totals()
+    else:
+        print_entries(by='function')
+        print_totals()
+
+if __name__ == "__main__":
+    import argparse
+    import sys
+    parser = argparse.ArgumentParser(
+        description="Show/manipulate coverage info")
+    parser.add_argument('gcovpaths', nargs='*',
+        help="Description of *.gcov files to use for coverage info. May be \
+            a directory or list of files. Coverage files will be merged to \
+            show the total coverage. Defaults to \"%s\"." % RESULTDIR)
+    parser.add_argument('--results', default=RESULTDIR,
+        help="Directory to store results. Created implicitly. Used if \
+            annotated files are requested. Defaults to \"%s\"." % RESULTDIR)
+    parser.add_argument('--merge',
+        help="Merge coverage info into the specified file, writing the \
+            cumulative coverage info to the file. The output from this script \
+            does not include the coverage from the merge file.")
+    parser.add_argument('--filter',
+        help="Specify files with care about, all other coverage info (system \
+            headers, test framework, etc) will be discarded.")
+    parser.add_argument('--annotate', action='store_true',
+        help="Output annotated source files into the result directory. Each \
+            line will be annotated with the number of hits during testing. \
+            This is useful for finding out which lines do not have test \
+            coverage.")
+    parser.add_argument('-v', '--verbose', action='store_true',
+        help="Output commands that run behind the scenes.")
+    parser.add_argument('-i', '--input',
+        help="Don't do any work, instead use this CSV file.")
+    parser.add_argument('-o', '--output',
+        help="Specify CSV file to store results.")
+    parser.add_argument('-d', '--diff',
+        help="Specify CSV file to diff code size against.")
+    parser.add_argument('-a', '--all', action='store_true',
+        help="Show all functions, not just the ones that changed.")
+    parser.add_argument('--files', action='store_true',
+        help="Show file-level coverage.")
+    parser.add_argument('-s', '--summary', action='store_true',
+        help="Only show the total coverage.")
+    parser.add_argument('-S', '--status', action='store_true',
+        help="Show minimum info useful for a single-line status.")
+    parser.add_argument('-q', '--quiet', action='store_true',
+        help="Don't show anything, useful with -o.")
+    sys.exit(main(**vars(parser.parse_args())))

scripts/test.py

@@ -21,19 +21,37 @@ import errno
 import signal
 
 TESTDIR = 'tests'
+RESULTDIR = 'results' # only used for coverage
 RULES = """
 define FLATTEN
-tests/%$(subst /,.,$(target)): $(target)
+%(path)s%%$(subst /,.,$(target)): $(target)
     ./scripts/explode_asserts.py $$< -o $$@
 endef
 $(foreach target,$(SRC),$(eval $(FLATTEN)))
 
--include tests/*.d
+-include %(path)s*.d
-
 .SECONDARY:
-%.test: %.test.o $(foreach f,$(subst /,.,$(OBJ)),%.$f)
+
+%(path)s.test: %(path)s.test.o $(foreach t,$(subst /,.,$(OBJ)),%(path)s.$t)
     $(CC) $(CFLAGS) $^ $(LFLAGS) -o $@
 """
+COVERAGE_TEST_RULES = """
+%(path)s.test: override CFLAGS += -fprofile-arcs -ftest-coverage
+
+# delete lingering coverage info during build
+%(path)s.test: | %(path)s.test.clean
+.PHONY: %(path)s.test.clean
+%(path)s.test.clean:
+    rm -f %(path)s*.gcda
+
+override TEST_GCDAS += %(path)s*.gcda
+"""
+COVERAGE_RESULT_RULES = """
+# dependencies defined in test makefiles
+.PHONY: %(results)s/coverage.gcov
+%(results)s/coverage.gcov: $(patsubst %%,%%.gcov,$(wildcard $(TEST_GCDAS)))
+    ./scripts/coverage.py -s $^ --filter="$(SRC)" --merge=$@
+"""
 GLOBALS = """
 //////////////// AUTOGENERATED TEST ////////////////
 #include "lfs.h"
@@ -516,13 +534,20 @@ class TestSuite:
 
         # write makefiles
         with open(self.path + '.mk', 'w') as mk:
-            mk.write(RULES.replace(4*' ', '\t'))
+            mk.write(RULES.replace(4*' ', '\t') % dict(path=self.path))
             mk.write('\n')
 
+            # add coverage hooks?
+            if args.get('coverage', False):
+                mk.write(COVERAGE_TEST_RULES.replace(4*' ', '\t') % dict(
+                    results=args['results'],
+                    path=self.path))
+                mk.write('\n')
+
             # add truely global defines globally
             for k, v in sorted(self.defines.items()):
-                mk.write('%s: override CFLAGS += -D%s=%r\n' % (
+                mk.write('%s.test: override CFLAGS += -D%s=%r\n'
-                    self.path+'.test', k, v))
+                    % (self.path, k, v))
 
             for path in tfs:
                 if path is None:
@@ -596,7 +621,7 @@ def main(**args):
 
         # figure out the suite's toml file
         if os.path.isdir(testpath):
-            testpath = testpath + '/test_*.toml'
+            testpath = testpath + '/*.toml'
         elif os.path.isfile(testpath):
             testpath = testpath
         elif testpath.endswith('.toml'):
@@ -674,12 +699,12 @@ def main(**args):
         sum(len(suite.cases) for suite in suites),
         sum(len(suite.perms) for suite in suites)))
 
-    filtered = 0
+    total = 0
     for suite in suites:
         for perm in suite.perms:
-            filtered += perm.shouldtest(**args)
+            total += perm.shouldtest(**args)
-    if filtered != sum(len(suite.perms) for suite in suites):
+    if total != sum(len(suite.perms) for suite in suites):
-        print('filtered down to %d permutations' % filtered)
+        print('total down to %d permutations' % total)
 
     # only requested to build?
     if args.get('build', False):
@@ -723,6 +748,45 @@ def main(**args):
                 sys.stdout.write('\n')
                 failed += 1
 
+    if args.get('coverage', False):
+        # mkdir -p resultdir
+        os.makedirs(args['results'], exist_ok=True)
+
+        # collect coverage info
+        hits, branches = 0, 0
+
+        with open(args['results'] + '/coverage.mk', 'w') as mk:
+            mk.write(COVERAGE_RESULT_RULES.replace(4*' ', '\t') % dict(
+                results=args['results']))
+
+        cmd = (['make', '-f', 'Makefile'] +
+            list(it.chain.from_iterable(['-f', m] for m in makefiles)) +
+            ['-f', args['results'] + '/coverage.mk',
+                args['results'] + '/coverage.gcov'])
+        mpty, spty = pty.openpty()
+        if args.get('verbose', False):
+            print(' '.join(shlex.quote(c) for c in cmd))
+        proc = sp.Popen(cmd, stdout=spty)
+        os.close(spty)
+        mpty = os.fdopen(mpty, 'r', 1)
+        while True:
+            try:
+                line = mpty.readline()
+            except OSError as e:
+                if e.errno == errno.EIO:
+                    break
+                raise
+            if args.get('verbose', False):
+                sys.stdout.write(line)
+            # get coverage status
+            m = re.match('^TOTALS +([0-9]+)/([0-9]+)', line)
+            if m:
+                hits = int(m.group(1))
+                branches = int(m.group(2))
+        proc.wait()
+        if proc.returncode != 0:
+            sys.exit(-3)
+
     if args.get('gdb', False):
         failure = None
         for suite in suites:
@@ -735,8 +799,13 @@ def main(**args):
             failure.case.test(failure=failure, **args)
             sys.exit(0)
 
-    print('tests passed: %d' % passed)
+    print('tests passed %d/%d (%.2f%%)' % (passed, total,
-    print('tests failed: %d' % failed)
+        100*(passed/total if total else 1.0)))
+    print('tests failed %d/%d (%.2f%%)' % (failed, total,
+        100*(failed/total if total else 1.0)))
+    if args.get('coverage', False):
+        print('coverage %d/%d (%.2f%%)' % (hits, branches,
+            100*(hits/branches if branches else 1.0)))
     return 1 if failed > 0 else 0
 
 if __name__ == "__main__":
@@ -749,6 +818,9 @@ if __name__ == "__main__":
             directory of tests, a specific file, a suite by name, and even a \
             specific test case by adding brackets. For example \
             \"test_dirs[0]\" or \"{0}/test_dirs.toml[0]\".".format(TESTDIR))
+    parser.add_argument('--results', default=RESULTDIR,
+        help="Directory to store results. Created implicitly. Only used in \
+            this script for coverage information if --coverage is provided.")
     parser.add_argument('-D', action='append', default=[],
         help="Overriding parameter definitions.")
     parser.add_argument('-v', '--verbose', action='store_true',
@@ -769,10 +841,15 @@ if __name__ == "__main__":
         help="Run tests normally.")
     parser.add_argument('-r', '--reentrant', action='store_true',
         help="Run reentrant tests with simulated power-loss.")
-    parser.add_argument('-V', '--valgrind', action='store_true',
+    parser.add_argument('--valgrind', action='store_true',
         help="Run non-leaky tests under valgrind to check for memory leaks.")
-    parser.add_argument('-e', '--exec', default=[], type=lambda e: e.split(),
+    parser.add_argument('--exec', default=[], type=lambda e: e.split(),
         help="Run tests with another executable prefixed on the command line.")
-    parser.add_argument('-d', '--disk',
+    parser.add_argument('--disk',
         help="Specify a file to use for persistent/reentrant tests.")
+    parser.add_argument('--coverage', action='store_true',
+        help="Collect coverage information across tests. This is stored in \
+            the results directory. Coverage is not reset between runs \
+            allowing multiple test runs to contribute to coverage \
+            information.")
     sys.exit(main(**vars(parser.parse_args())))