test: add automatic unit test coverage generation

Using lcov, generate an HTML report via "make coverage-report"
describing the coverage of each file. Ideally, this will get added to
an automated testing pipeline.

Signed-off-by: Max Regan <mgregan2@gmail.com>

Makefile

@@ -1,4 +1,5 @@
 OUT=build
+COV_DIR=$(OUT)/coverage/
 SRC_DIR=src
 APP_DIR=src/apps/
 
@@ -55,10 +56,8 @@ gbasm: $(OUT)/apps/gbasm
 
 .PHONY: gbasm-test sample-test tests
 
-gbasm-test: $(OUT)/apps/gbasm-test
-sample-test: $(OUT)/apps/sample-test
-tri-test: $(OUT)/apps/tri-test
-tests: gbasm-test sample-test tri-test
+TESTS=$(OUT)/apps/gbasm-test $(OUT)/apps/tri-test
+tests: $(TESTS)
 
 $(ALL_APPS) $(ALL_OBJS): $(CONFIG)
 
@@ -73,7 +72,48 @@ $(APPS): $(OBJS) $$@.o
 	@$(shell mkdir -p $(@D))
 	@$(CC) $^ $(LDFLAGS) -o $@
 
-.PHONY: clean realclean
+
+.PHONY: check cov-report
+
+define run_tests =
+	@for i in $(TESTS); do \
+		$$i; \
+		if [ $$? -ne 0 ]; then \
+			exit 1; \
+		fi; \
+	done;
+endef
+
+.PHONY: check coverage coverage-report
+
+check: $(TESTS)
+	$(run_tests)
+
+
+COV_BASE=$(COV_DIR)/cov_base.info
+.PHONY: $(COV_BASE)
+
+
+$(COV_BASE):
+	@mkdir -p $(COV_DIR)
+	@lcov -c -i -d $(OUT) -o $(COV_BASE)
+
+$(COV_DIR)/coverage.info coverage: $(TESTS) $(COV_BASE)
+	@for test in $(TESTS); do \
+		$$test; \
+		lcov -c -d $(OUT) -o $(COV_DIR)/$$(basename $$test).info -t $$(basename $$test); \
+	done
+	lcov $$(for i in $$(ls -1 $(COV_DIR)/*.info); do echo "-a $$i"; done) -o $(COV_DIR)/coverage.info
+
+coverage-report: coverage
+	@mkdir -p $(COV_DIR)/html/
+	@genhtml --prefix $(PWD) --output-directory=$(COV_DIR)/html $(COV_DIR)/coverage.info
+
+.PHONY: clean realclean cov-clean
+cov-clean:
+	@find $(OUT)/ \( -iname *.gcno -o -iname *.gcda \) -delete
+	@rm
+
 clean:
 	@rm -f $(ALL_OBJS) $(APPS)