diff --git a/metrics_test.go b/metrics_test.go
new file mode 100644
index 000000000..760d62e02
--- /dev/null
+++ b/metrics_test.go
@@ -0,0 +1,394 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddy
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+)
+
+func TestGlobalMetrics_ConfigSuccess(t *testing.T) {
+	// Test setting config success metric
+	originalValue := getMetricValue(globalMetrics.configSuccess)
+
+	// Set to success
+	globalMetrics.configSuccess.Set(1)
+	newValue := getMetricValue(globalMetrics.configSuccess)
+
+	if newValue != 1 {
+		t.Errorf("Expected config success metric to be 1, got %f", newValue)
+	}
+
+	// Set to failure
+	globalMetrics.configSuccess.Set(0)
+	failureValue := getMetricValue(globalMetrics.configSuccess)
+
+	if failureValue != 0 {
+		t.Errorf("Expected config success metric to be 0, got %f", failureValue)
+	}
+
+	// Restore original value if it existed
+	if originalValue != 0 {
+		globalMetrics.configSuccess.Set(originalValue)
+	}
+}
+
+func TestGlobalMetrics_ConfigSuccessTime(t *testing.T) {
+	// Set success time
+	globalMetrics.configSuccessTime.SetToCurrentTime()
+
+	// Get the metric value
+	metricValue := getMetricValue(globalMetrics.configSuccessTime)
+
+	// Should be a reasonable Unix timestamp (not zero)
+	if metricValue == 0 {
+		t.Error("Config success time should not be zero")
+	}
+
+	// Should be recent (within last minute)
+	now := time.Now().Unix()
+	if int64(metricValue) < now-60 || int64(metricValue) > now {
+		t.Errorf("Config success time %f should be recent (now: %d)", metricValue, now)
+	}
+}
+
+func TestAdminMetrics_RequestCount(t *testing.T) {
+	// Initialize admin metrics for testing
+	initAdminMetrics()
+
+	labels := prometheus.Labels{
+		"handler": "test",
+		"path":    "/config",
+		"method":  "GET",
+		"code":    "200",
+	}
+
+	// Get initial value
+	initialValue := getCounterValue(adminMetrics.requestCount, labels)
+
+	// Increment counter
+	adminMetrics.requestCount.With(labels).Inc()
+
+	// Verify increment
+	newValue := getCounterValue(adminMetrics.requestCount, labels)
+	if newValue != initialValue+1 {
+		t.Errorf("Expected counter to increment by 1, got %f -> %f", initialValue, newValue)
+	}
+}
+
+func TestAdminMetrics_RequestErrors(t *testing.T) {
+	// Initialize admin metrics for testing
+	initAdminMetrics()
+
+	labels := prometheus.Labels{
+		"handler": "test",
+		"path":    "/test",
+		"method":  "POST",
+	}
+
+	// Get initial value
+	initialValue := getCounterValue(adminMetrics.requestErrors, labels)
+
+	// Increment error counter
+	adminMetrics.requestErrors.With(labels).Inc()
+
+	// Verify increment
+	newValue := getCounterValue(adminMetrics.requestErrors, labels)
+	if newValue != initialValue+1 {
+		t.Errorf("Expected error counter to increment by 1, got %f -> %f", initialValue, newValue)
+	}
+}
+
+func TestMetrics_ConcurrentAccess(t *testing.T) {
+	// Initialize admin metrics
+	initAdminMetrics()
+
+	const numGoroutines = 100
+	const incrementsPerGoroutine = 10
+
+	var wg sync.WaitGroup
+
+	labels := prometheus.Labels{
+		"handler": "concurrent",
+		"path":    "/concurrent",
+		"method":  "GET",
+		"code":    "200",
+	}
+
+	initialCount := getCounterValue(adminMetrics.requestCount, labels)
+
+	// Concurrent increments
+	for i := 0; i < numGoroutines; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for j := 0; j < incrementsPerGoroutine; j++ {
+				adminMetrics.requestCount.With(labels).Inc()
+			}
+		}()
+	}
+
+	wg.Wait()
+
+	// Verify final count
+	finalCount := getCounterValue(adminMetrics.requestCount, labels)
+	expectedIncrement := float64(numGoroutines * incrementsPerGoroutine)
+
+	if finalCount-initialCount != expectedIncrement {
+		t.Errorf("Expected counter to increase by %f, got %f",
+			expectedIncrement, finalCount-initialCount)
+	}
+}
+
+func TestMetrics_LabelValidation(t *testing.T) {
+	// Test various label combinations
+	tests := []struct {
+		name   string
+		labels prometheus.Labels
+		metric string
+	}{
+		{
+			name: "valid request count labels",
+			labels: prometheus.Labels{
+				"handler": "test",
+				"path":    "/api/test",
+				"method":  "GET",
+				"code":    "200",
+			},
+			metric: "requestCount",
+		},
+		{
+			name: "valid error labels",
+			labels: prometheus.Labels{
+				"handler": "test",
+				"path":    "/api/error",
+				"method":  "POST",
+			},
+			metric: "requestErrors",
+		},
+		{
+			name: "empty path",
+			labels: prometheus.Labels{
+				"handler": "test",
+				"path":    "",
+				"method":  "GET",
+				"code":    "404",
+			},
+			metric: "requestCount",
+		},
+		{
+			name: "special characters in path",
+			labels: prometheus.Labels{
+				"handler": "test",
+				"path":    "/api/test%20with%20spaces",
+				"method":  "PUT",
+				"code":    "201",
+			},
+			metric: "requestCount",
+		},
+	}
+
+	initAdminMetrics()
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			// This should not panic or error
+			switch test.metric {
+			case "requestCount":
+				adminMetrics.requestCount.With(test.labels).Inc()
+			case "requestErrors":
+				adminMetrics.requestErrors.With(test.labels).Inc()
+			}
+		})
+	}
+}
+
+func TestMetrics_Initialization_Idempotent(t *testing.T) {
+	// Test that initializing admin metrics multiple times is safe
+	for i := 0; i < 5; i++ {
+		func() {
+			defer func() {
+				if r := recover(); r != nil {
+					t.Errorf("Iteration %d: initAdminMetrics panicked: %v", i, r)
+				}
+			}()
+			initAdminMetrics()
+		}()
+	}
+}
+
+func TestInstrumentHandlerCounter(t *testing.T) {
+	// Create a test counter with the expected labels
+	counter := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "test_counter",
+			Help: "Test counter for instrumentation",
+		},
+		[]string{"code", "method"},
+	)
+
+	// Create instrumented handler
+	testHandler := instrumentHandlerCounter(
+		counter,
+		&mockHTTPHandler{statusCode: 200},
+	)
+
+	// Create test request
+	req := httptest.NewRequest("GET", "/test", nil)
+	rr := httptest.NewRecorder()
+
+	// Get initial counter value
+	initialValue := getCounterValue(counter, prometheus.Labels{"code": "200", "method": "GET"})
+
+	// Serve request
+	testHandler.ServeHTTP(rr, req)
+
+	// Verify counter was incremented
+	finalValue := getCounterValue(counter, prometheus.Labels{"code": "200", "method": "GET"})
+	if finalValue != initialValue+1 {
+		t.Errorf("Expected counter to increment by 1, got %f -> %f", initialValue, finalValue)
+	}
+}
+
+func TestInstrumentHandlerCounter_ErrorStatus(t *testing.T) {
+	counter := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "test_error_counter",
+			Help: "Test counter for error status",
+		},
+		[]string{"code", "method"},
+	)
+
+	// Test different status codes
+	statusCodes := []int{200, 404, 500, 301, 401}
+
+	for _, status := range statusCodes {
+		t.Run(fmt.Sprintf("status_%d", status), func(t *testing.T) {
+			handler := instrumentHandlerCounter(
+				counter,
+				&mockHTTPHandler{statusCode: status},
+			)
+
+			req := httptest.NewRequest("GET", "/test", nil)
+			rr := httptest.NewRecorder()
+
+			statusLabels := prometheus.Labels{"code": fmt.Sprintf("%d", status), "method": "GET"}
+			initialValue := getCounterValue(counter, statusLabels)
+
+			handler.ServeHTTP(rr, req)
+
+			finalValue := getCounterValue(counter, statusLabels)
+			if finalValue != initialValue+1 {
+				t.Errorf("Status %d: Expected counter increment", status)
+			}
+		})
+	}
+}
+
+// Helper functions
+func getMetricValue(gauge prometheus.Gauge) float64 {
+	metric := &dto.Metric{}
+	gauge.Write(metric)
+	return metric.GetGauge().GetValue()
+}
+
+func getCounterValue(counter *prometheus.CounterVec, labels prometheus.Labels) float64 {
+	metric, err := counter.GetMetricWith(labels)
+	if err != nil {
+		return 0
+	}
+
+	pb := &dto.Metric{}
+	metric.Write(pb)
+	return pb.GetCounter().GetValue()
+}
+
+type mockHTTPHandler struct {
+	statusCode int
+}
+
+func (m *mockHTTPHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(m.statusCode)
+}
+
+func TestMetrics_Memory_Usage(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping memory test in short mode")
+	}
+
+	// Initialize metrics
+	initAdminMetrics()
+
+	// Create many different label combinations
+	const numLabels = 1000
+
+	for i := 0; i < numLabels; i++ {
+		labels := prometheus.Labels{
+			"handler": fmt.Sprintf("handler_%d", i%10),
+			"path":    fmt.Sprintf("/path_%d", i),
+			"method":  []string{"GET", "POST", "PUT", "DELETE"}[i%4],
+			"code":    []string{"200", "404", "500"}[i%3],
+		}
+
+		adminMetrics.requestCount.With(labels).Inc()
+
+		// Also increment error counter occasionally
+		if i%10 == 0 {
+			errorLabels := prometheus.Labels{
+				"handler": labels["handler"],
+				"path":    labels["path"],
+				"method":  labels["method"],
+			}
+			adminMetrics.requestErrors.With(errorLabels).Inc()
+		}
+	}
+
+	// Test passes if we don't run out of memory or panic
+}
+
+func BenchmarkGlobalMetrics_ConfigSuccess(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		globalMetrics.configSuccess.Set(float64(i % 2))
+	}
+}
+
+func BenchmarkGlobalMetrics_ConfigSuccessTime(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		globalMetrics.configSuccessTime.SetToCurrentTime()
+	}
+}
+
+func BenchmarkAdminMetrics_RequestCount_WithLabels(b *testing.B) {
+	initAdminMetrics()
+
+	labels := prometheus.Labels{
+		"handler": "benchmark",
+		"path":    "/benchmark",
+		"method":  "GET",
+		"code":    "200",
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		adminMetrics.requestCount.With(labels).Inc()
+	}
+}