diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..9cda93d
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,182 @@
+package main
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/api/types/container"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// mockContainerClient implements a minimal mock for docker client operations
+type mockContainerClient struct {
+	containers []types.Container
+	infos      map[string]types.ContainerJSON
+}
+
+func (m *mockContainerClient) ContainerList(ctx context.Context, options container.ListOptions) ([]types.Container, error) {
+	return m.containers, nil
+}
+
+func (m *mockContainerClient) ContainerInspect(ctx context.Context, containerID string) (types.ContainerJSON, error) {
+	return m.infos[containerID], nil
+}
+
+// TestHealthyEndpoint tests the /-/healthy endpoint without starting the server
+func TestHealthyEndpoint(t *testing.T) {
+	req := httptest.NewRequest("GET", "/-/healthy", nil)
+	w := httptest.NewRecorder()
+
+	testHandler := http.NewServeMux()
+	testHandler.HandleFunc("/-/healthy", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("up"))
+	})
+
+	testHandler.ServeHTTP(w, req)
+
+	result := w.Result()
+	body, _ := io.ReadAll(result.Body)
+
+	if result.StatusCode != http.StatusOK {
+		t.Errorf("expected status 200, got %d", result.StatusCode)
+	}
+
+	if !strings.Contains(string(body), "up") {
+		t.Errorf("expected 'up' in response, got: %s", string(body))
+	}
+}
+
+// TestRootEndpoint tests the root endpoint without starting the server
+func TestRootEndpoint(t *testing.T) {
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+
+	testHandler := http.NewServeMux()
+	testHandler.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/html")
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("<h1>docker state exporter</h1>"))
+	})
+
+	testHandler.ServeHTTP(w, req)
+
+	result := w.Result()
+	body, _ := io.ReadAll(result.Body)
+
+	if result.StatusCode != http.StatusOK {
+		t.Errorf("expected status 200, got %d", result.StatusCode)
+	}
+
+	if !strings.Contains(string(body), "docker state exporter") {
+		t.Errorf("expected 'docker state exporter' in response, got: %s", string(body))
+	}
+}
+
+// TestDockerHealthCollectorWithMockedClient tests collector can gather container states
+func TestDockerHealthCollectorWithMockedClient(t *testing.T) {
+	mockClient := &mockContainerClient{
+		containers: []types.Container{
+			{
+				ID:    "test-container-1",
+				Names: []string{"/test1"},
+				Image: "test-image:latest",
+			},
+		},
+		infos: map[string]types.ContainerJSON{
+			"test-container-1": {
+				ContainerJSONBase: &types.ContainerJSONBase{
+					ID: "test-container-1",
+					State: &types.ContainerState{
+						Status:     "running",
+						OOMKilled:  false,
+						StartedAt:  "2024-01-01T00:00:00Z",
+						FinishedAt: "0001-01-01T00:00:00Z",
+					},
+				},
+				Config: &container.Config{
+					Image: "test-image:latest",
+					Labels: map[string]string{
+						"test-label": "test-value",
+					},
+				},
+			},
+		},
+	}
+
+	collector := &dockerHealthCollector{
+		containerClient: mockClient,
+	}
+
+	// Call collectContainer to fetch from mock
+	collector.collectContainer()
+
+	// Verify cache was populated
+	if len(collector.containerInfoCache) != 1 {
+		t.Errorf("expected 1 container in cache, got %d", len(collector.containerInfoCache))
+	}
+
+	if collector.containerInfoCache[0].ID != "test-container-1" {
+		t.Errorf("expected container ID 'test-container-1', got '%s'", collector.containerInfoCache[0].ID)
+	}
+
+	if collector.containerInfoCache[0].Config.Image != "test-image:latest" {
+		t.Errorf("expected image 'test-image:latest', got '%s'", collector.containerInfoCache[0].Config.Image)
+	}
+}
+
+// TestCollectMetrics tests that metrics are collected properly from container info
+func TestCollectMetrics(t *testing.T) {
+	mockClient := &mockContainerClient{
+		containers: []types.Container{
+			{
+				ID:    "test-container-1",
+				Names: []string{"/test1"},
+				Image: "test-image:latest",
+			},
+		},
+		infos: map[string]types.ContainerJSON{
+			"test-container-1": {
+				ContainerJSONBase: &types.ContainerJSONBase{
+					ID: "test-container-1",
+					State: &types.ContainerState{
+						Status:     "running",
+						OOMKilled:  false,
+						StartedAt:  "2024-01-01T00:00:00.000000000Z",
+						FinishedAt: "0001-01-01T00:00:00.000000000Z",
+						Health:     nil,
+					},
+					RestartCount: 0,
+				},
+				Config: &container.Config{
+					Image: "test-image:latest",
+					Labels: map[string]string{
+						"app": "test",
+					},
+				},
+			},
+		},
+	}
+
+	collector := &dockerHealthCollector{
+		containerClient: mockClient,
+	}
+
+	collector.collectContainer()
+
+	// Collect metrics
+	ch := make(chan prometheus.Metric, 100)
+	defer close(ch)
+
+	// This should not panic when collecting metrics
+	collector.collectMetrics(ch)
+
+	if len(collector.containerInfoCache) != 1 {
+		t.Errorf("expected 1 container, got %d", len(collector.containerInfoCache))
+	}
+}