Don't run cover when there's no ebin files in the directory

plugins/eunit.mk

@@ -21,20 +21,25 @@ help::
 # Plugin-specific targets.
 
 define eunit.erl
-	case "$(COVER)" of
-		"" -> ok;
+	Enabled = case "$(COVER)" of
+		"" -> false;
 		_ ->
-			case cover:compile_beam_directory("ebin") of
-				{error, _} -> halt(1);
-				_ -> ok
+			case filelib:is_dir("ebin") of
+				false -> false;
+				true ->
+					case cover:compile_beam_directory("ebin") of
+						{error, _} -> halt(1);
+						_ -> true
+					end
 			end
 	end,
 	case eunit:test($1, [$(EUNIT_OPTS)]) of
 		ok -> ok;
 		error -> halt(2)
 	end,
-	case "$(COVER)" of
-		"" -> ok;
+	case {Enabled, "$(COVER)"} of
+		{false, _} -> ok;
+		{_, ""} -> ok;
 		_ ->
 			cover:export("$(COVER_DATA_DIR)/eunit.coverdata")
 	end,

test/plugin_cover.mk

@@ -1,6 +1,6 @@
 # Common Test plugin.
 
-COVER_CASES = ct custom-dir eunit report-and-merge
+COVER_CASES = ct custom-dir eunit eunit-apps-only report-and-merge
 COVER_TARGETS = $(addprefix cover-,$(COVER_CASES))
 
 .PHONY: cover $(COVER_TARGETS)
@@ -115,6 +115,33 @@ cover-eunit: build clean
 	$t $(MAKE) -C $(APP) clean $v
 	$t test ! -e $(APP)/eunit.coverdata
 
+cover-eunit-apps-only: build clean
+
+	$i "Create a multi application repository with no root application"
+	$t mkdir $(APP)/
+	$t cp ../erlang.mk $(APP)/
+	$t echo "include erlang.mk" > $(APP)/Makefile
+
+	$i "Create a new application named my_app"
+	$t $(MAKE) -C $(APP) new-app in=my_app $v
+
+	$i "Generate a module containing EUnit tests in my_app"
+	$t printf "%s\n" \
+		"-module(my_app)." \
+		"-ifdef(TEST)." \
+		"-include_lib(\"eunit/include/eunit.hrl\")." \
+		"ok_test() -> ok." \
+		"-endif." > $(APP)/apps/my_app/src/my_app.erl
+
+	$i "Run EUnit with code coverage enabled"
+	$t $(MAKE) -C $(APP) eunit COVER=1 $v
+
+	$i "Check that no file was generated in the top-level directory"
+	$t ! test -f $(APP)/eunit.coverdata
+
+	$i "Check that the generated file exists"
+	$t test -f $(APP)/apps/my_app/eunit.coverdata
+
 cover-report-and-merge: build clean
 
 	$i "Bootstrap a new OTP application named $(APP)"