From e7653f29ebed92f852aa55e4b399884ff8132bd7 Mon Sep 17 00:00:00 2001
From: Theron Voran <tvoran@users.noreply.github.com>
Date: Mon, 2 Dec 2024 12:43:34 -0800
Subject: [PATCH] Add metrics unit test (#709)

* Add metrics unit test

* go mod tidy
---
 agent-inject/metrics_test.go | 67 ++++++++++++++++++++++++++++++++++++
 go.mod                       |  1 +
 2 files changed, 68 insertions(+)
 create mode 100644 agent-inject/metrics_test.go

diff --git a/agent-inject/metrics_test.go b/agent-inject/metrics_test.go
new file mode 100644
index 00000000..65101877
--- /dev/null
+++ b/agent-inject/metrics_test.go
@@ -0,0 +1,67 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package agent_inject
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/testutil"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_incrementInjections(t *testing.T) {
+	MustRegisterInjectorMetrics(prometheus.DefaultRegisterer)
+
+	tests := map[string]struct {
+		namespace      string
+		mutateResponse MutateResponse
+		expectedLabels map[string]string
+	}{
+		"init_only": {
+			namespace: "init",
+			mutateResponse: MutateResponse{
+				InjectedInit:    true,
+				InjectedSidecar: false,
+			},
+			expectedLabels: map[string]string{
+				metricsLabelNamespace: "init",
+				metricsLabelType:      metricsLabelTypeInitOnly,
+			},
+		},
+		"sidecar_only": {
+			namespace: "sidecar",
+			mutateResponse: MutateResponse{
+				InjectedInit:    false,
+				InjectedSidecar: true,
+			},
+			expectedLabels: map[string]string{
+				metricsLabelNamespace: "sidecar",
+				metricsLabelType:      metricsLabelTypeSidecarOnly,
+			},
+		},
+		"init_and_sidecar": {
+			namespace: "both",
+			mutateResponse: MutateResponse{
+				InjectedInit:    true,
+				InjectedSidecar: true,
+			},
+			expectedLabels: map[string]string{
+				metricsLabelNamespace: "both",
+				metricsLabelType:      metricsLabelTypeBoth,
+			},
+		},
+	}
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			t.Cleanup(func() {
+				injectionsByNamespace.Reset()
+			})
+			incrementInjections(test.namespace, test.mutateResponse)
+			assert.Equal(t, 1, testutil.CollectAndCount(injectionsByNamespace))
+			check := injectionsByNamespace.With(prometheus.Labels(test.expectedLabels))
+			assert.Equal(t, float64(1), testutil.ToFloat64(check))
+		})
+	}
+}
diff --git a/go.mod b/go.mod
index ec219ce3..2b75a430 100644
--- a/go.mod
+++ b/go.mod
@@ -58,6 +58,7 @@ require (
 	github.com/josharian/intern v1.0.0 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/compress v1.17.9 // indirect
+	github.com/kylelemons/godebug v1.1.0 // indirect
 	github.com/mailru/easyjson v0.7.7 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect