fix make c on macos

Makefile

@@ -14,7 +14,7 @@ f: ## Format code
 c: ## Measure code coverage
 	go test -race -covermode=atomic ./... -coverprofile=cover.out && \
 	go tool cover -func cover.out \
-		| grep -vP '[89]\d\.\d%' | grep -v '100.0%' \
+		| grep -v '100.0%' \
 		|| true
 
 	rm cover.out

configuration_test.go

@@ -16,3 +16,8 @@ func Test_Configuration_BucketsPowerOf2(t *testing.T) {
 		}
 	}
 }
+
+func Test_Configuration_Buffers(t *testing.T) {
+	assert.Equal(t, Configure[int]().DeleteBuffer(24).deleteBuffer, 24)
+	assert.Equal(t, Configure[int]().PromoteBuffer(95).promoteBuffer, 95)
+}