Add integration test to verify setting a custom idempotency key works

tests/Mollie.Tests.Integration/Api/PaymentTests.cs

@@ -102,6 +102,26 @@ public async Task CanCreateDefaultPaymentWithOnlyRequiredFields() {
         result.Description.Should().Be(paymentRequest.Description);
         result.RedirectUrl.Should().Be(paymentRequest.RedirectUrl);
     }
+
+    [DefaultRetryFact]
+    public async Task CanCreateDefaultPaymentWithCustomIdempotencyKey() {
+        // Given: we create a payment request with only the required parameters
+        PaymentRequest paymentRequest = new PaymentRequest() {
+            Amount = new Amount(Currency.EUR, "100.00"),
+            Description = "Description",
+            RedirectUrl = DefaultRedirectUrl
+        };
+
+        // When: We send the payment request to Mollie
+        using (_paymentClient.WithIdempotencyKey("my-idempotency-key"))
+        {
+            PaymentResponse firstAttempt = await _paymentClient.CreatePaymentAsync(paymentRequest);
+            PaymentResponse secondAttempt = await _paymentClient.CreatePaymentAsync(paymentRequest);
+
+            // Then: Make sure the responses have the same payment Id
+            firstAttempt.Id.Should().Be(secondAttempt.Id);
+        }
+    }
 
     [DefaultRetryFact]
     public async Task CanCreateDefaultPaymentWithAllFields() {

tests/Mollie.Tests.Unit/Client/PaymentClientTests.cs

@@ -27,17 +27,25 @@ public async Task CreatePaymentAsync_WithCustomIdempotencyKey_CustomIdemPotencyK
             Description = "Description",
             RedirectUrl = "http://www.mollie.com"
         };
-        const string customIdempotencyKey = "my-idempotency-key";
+        const string customIdempotencyKey1 = "my-idempotency-key-1";
+        const string customIdempotencyKey2 = "my-idempotency-key-2";
         const string jsonToReturnInMockResponse = defaultPaymentJsonResponse;
         var mockHttp = new MockHttpMessageHandler();
         mockHttp.Expect(HttpMethod.Post, $"{BaseMollieClient.ApiEndPoint}*")
-            .WithHeaders("Idempotency-Key", customIdempotencyKey)
+            .WithHeaders("Idempotency-Key", customIdempotencyKey1)
+            .Respond("application/json", jsonToReturnInMockResponse);
+        mockHttp.Expect(HttpMethod.Post, $"{BaseMollieClient.ApiEndPoint}*")
+            .WithHeaders("Idempotency-Key", customIdempotencyKey2)
             .Respond("application/json", jsonToReturnInMockResponse);
         HttpClient httpClient = mockHttp.ToHttpClient();
         PaymentClient paymentClient = new PaymentClient("abcde", httpClient);
 
         // Act
-        using (paymentClient.WithIdempotencyKey(customIdempotencyKey))
+        using (paymentClient.WithIdempotencyKey(customIdempotencyKey1))
+        {
+            await paymentClient.CreatePaymentAsync(paymentRequest);
+        }
+        using (paymentClient.WithIdempotencyKey(customIdempotencyKey2))
         {
             await paymentClient.CreatePaymentAsync(paymentRequest);
         }