diff --git a/api/client_test.go b/api/client_test.go
new file mode 100644
index 0000000..f1778e9
--- /dev/null
+++ b/api/client_test.go
@@ -0,0 +1,36 @@
+package api
+
+import (
+	"net/http"
+	"testing"
+)
+
+func TestNewClient(t *testing.T) {
+	apiKey := "test-api-key"
+	client := NewClient(apiKey)
+
+	if client.apiKey != apiKey {
+		t.Errorf("expected apiKey to be %s, got %s", apiKey, client.apiKey)
+	}
+
+	if client.baseURL != "https://console.vast.ai/api/v0" {
+		t.Errorf("expected baseURL to be %s, got %s", "https://console.vast.ai/api/v0", client.baseURL)
+	}
+
+	if client.httpClient == nil {
+		t.Error("expected httpClient to be initialized")
+	}
+}
+
+func TestApply(t *testing.T) {
+	apiKey := "abc123"
+	client := NewClient(apiKey)
+	req, _ := http.NewRequest("GET", "http://example.com", nil)
+
+	client.Apply(req)
+
+	expected := "Bearer " + apiKey
+	if got := req.Header.Get("Authorization"); got != expected {
+		t.Errorf("expected Authorization header to be %s, got %s", expected, got)
+	}
+}
diff --git a/api/instances_test.go b/api/instances_test.go
new file mode 100644
index 0000000..9938ef8
--- /dev/null
+++ b/api/instances_test.go
@@ -0,0 +1,23 @@
+//go:build real
+
+package api
+
+import (
+	"testing"
+)
+
+func GetInstancesTest(t *testing.T) {
+	// Create a new client with the test server's URL
+	client := NewClient("test")
+
+	// Call the GetInstances method
+	resp, err := client.GetInstances()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Ensure the response is valid
+	if len(resp.Instances) != 0 {
+		t.Fatalf("expected 0 instances, got %d", len(resp.Instances))
+	}
+}