Improve unit test coverage (#984)

* add tests for config

* add audio tests

* lint

* lint

* lint

config_test.go

@@ -100,3 +100,24 @@ func TestDefaultAnthropicConfigWithEmptyValues(t *testing.T) {
 		t.Errorf("Expected BaseURL to be %v, got %v", expectedBaseURL, config.BaseURL)
 	}
 }
+
+func TestClientConfigString(t *testing.T) {
+	// String() should always return the constant value
+	conf := openai.DefaultConfig("dummy-token")
+	expected := "<OpenAI API ClientConfig>"
+	got := conf.String()
+	if got != expected {
+		t.Errorf("ClientConfig.String() = %q; want %q", got, expected)
+	}
+}
+
+func TestGetAzureDeploymentByModel_NoMapper(t *testing.T) {
+	// On a zero-value or DefaultConfig, AzureModelMapperFunc is nil,
+	// so GetAzureDeploymentByModel should just return the input model.
+	conf := openai.DefaultConfig("dummy-token")
+	model := "some-model"
+	got := conf.GetAzureDeploymentByModel(model)
+	if got != model {
+		t.Errorf("GetAzureDeploymentByModel(%q) = %q; want %q", model, got, model)
+	}
+}