diff --git a/Makefile b/Makefile
index 06f8525..3c63603 100644
--- a/Makefile
+++ b/Makefile
@@ -121,13 +121,22 @@
 
 ## -----------------------------------------------------------------------
 ## -----------------------------------------------------------------------
+coverage-out := ./tests/results/go-test-coverage.out
+coverage-xml := ./tests/results/go-test-coverage.xml
+
+results-out  := ./tests/results/go-test-results.out
+results-xml  := ./tests/results/go-test-results.xml
+
 test-unit: clean local-omci-lib-go # @HELP Execute unit tests
 	@echo "Running unit tests..."
 	@mkdir -p ./tests/results
-	@${GO} test -mod=vendor -bench=. -v -coverprofile ./tests/results/go-test-coverage.out -covermode count ./... 2>&1 | tee ./tests/results/go-test-results.out ;\
+	@${GO} test -mod=vendor -bench=. -v \
+	  -coverprofile $(coverage-out) \
+	  -covermode count ./... \
+	  2>&1 | tee $(results-out) ;\
 	RETURN=$$? ;\
-	${GO_JUNIT_REPORT} < ./tests/results/go-test-results.out > ./tests/results/go-test-results.xml ;\
-	${GOCOVER_COBERTURA} < ./tests/results/go-test-coverage.out > ./tests/results/go-test-coverage.xml ;\
+	${GO_JUNIT_REPORT}   < $(results-out)  > $(results-xml) ;\
+	${GOCOVER_COBERTURA} < $(coverage-out) > $(coverage-xml) ;\
 	exit $$RETURN
 
 ## -----------------------------------------------------------------------
@@ -139,6 +148,12 @@
 	docker $(RM) -f bbsim
 
 ## -----------------------------------------------------------------------
+## Intgent: Update sources in the vendor/ directory.
+## Todo:
+##   o chicken-n-egg problem:
+##     - vendor/ is under revision control
+##     - go mod tidy will delete vendor
+##     - sandbox left unbuildable when mod-update target fails.
 ## -----------------------------------------------------------------------
 mod-update: # @HELP Download the dependencies to the vendor folder
 	${GO} mod tidy
@@ -238,6 +253,12 @@
 	@$(RM) -r tools/bin
 	@$(RM) -r release
 
+	@$(RM) $(coverage-out)
+	@$(RM) $(coverage-xml)
+
+	@$(RM) $(results-out)
+	@$(RM) $(results-xml)
+
 sterile :: clean
 
 ## -----------------------------------------------------------------------
diff --git a/makefiles/tools.mk b/makefiles/tools.mk
index 03aeb9d..b1bab03 100644
--- a/makefiles/tools.mk
+++ b/makefiles/tools.mk
@@ -35,7 +35,7 @@
 ## --interactive: Attach streams if running interactively (!jenkins)
 ## --tty        : Attach stdout else jenkins::docker is silent.
 ## -----------------------------------------------------------------------
-is-stdin       = $(shell test -t 0 && { echo '--interactive' })
+is-stdin       = $(shell test -t 0 && { echo '--interactive'; })
 is-stdin       += --tty
 
 # Docker volume mounts: container:/app/release <=> localhost:{pwd}/release
diff --git a/tests/results/.gitignore b/tests/results/.gitignore
index d6b7ef3..28da4c4 100644
--- a/tests/results/.gitignore
+++ b/tests/results/.gitignore
@@ -1,2 +1,8 @@
+# -*- makefile -*-
+
 *
 !.gitignore
+*.out
+*.xml
+
+# [EOF]
\ No newline at end of file