diff --git a/pom.xml b/pom.xml
index d327bfe..99e169a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -125,6 +125,12 @@
             <artifactId>postgresql</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.instancio</groupId>
+            <artifactId>instancio-junit</artifactId>
+            <version>5.3.0</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/src/main/java/ch/dlmw/swisssignchallenge/controllers/SigningRequestDocumentController.java b/src/main/java/ch/dlmw/swisssignchallenge/controllers/SigningRequestDocumentController.java
index 9c186fb..b732726 100644
--- a/src/main/java/ch/dlmw/swisssignchallenge/controllers/SigningRequestDocumentController.java
+++ b/src/main/java/ch/dlmw/swisssignchallenge/controllers/SigningRequestDocumentController.java
@@ -34,10 +34,8 @@ public class SigningRequestDocumentController implements SigningRequestDocumentA
             signingRequestDocumentService.updateSigningRequestDocument(patchedDocument);
 
             return ResponseEntity.noContent().build();
-        } catch (JsonPatchException e) {
+        } catch (JsonPatchException | IOException e) {
             throw new IllegalArgumentException("Failed to apply patch", e);
-        } catch (IOException e) {
-            throw new RuntimeException("Failed to apply patch", e);
         }
     }
 
diff --git a/src/test/java/ch/dlmw/swisssignchallenge/SigningRequestDocumentControllerTests.java b/src/test/java/ch/dlmw/swisssignchallenge/SigningRequestDocumentControllerTests.java
new file mode 100644
index 0000000..bb0b705
--- /dev/null
+++ b/src/test/java/ch/dlmw/swisssignchallenge/SigningRequestDocumentControllerTests.java
@@ -0,0 +1,115 @@
+package ch.dlmw.swisssignchallenge;
+
+import ch.dlmw.swisssignchallenge.controllers.SigningRequestDocumentController;
+import ch.dlmw.swisssignchallenge.entities.SigningRequestDocument;
+import ch.dlmw.swisssignchallenge.services.SigningRequestDocumentService;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.instancio.Instancio;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.openapitools.model.PatchOperation;
+
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.UUID;
+
+import static org.instancio.Select.field;
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+@ExtendWith(MockitoExtension.class)
+public class SigningRequestDocumentControllerTests {
+    @Mock
+    private SigningRequestDocumentService signingRequestDocumentService;
+
+    @InjectMocks
+    private SigningRequestDocumentController signingRequestDocumentController;
+
+    @BeforeEach
+    public void setUp() {
+        var objectMapper = new ObjectMapper();
+        signingRequestDocumentController = new SigningRequestDocumentController(
+                signingRequestDocumentService,
+                null,
+                objectMapper
+        );
+    }
+
+    @Test
+    public void givenCorrectRequest_whenPatchSigningRequestDocument_thenPatchDocument() {
+        var id = UUID.randomUUID();
+        var patchOperations = List.of(
+                new PatchOperation("replace", "/confirmed", "true")
+        );
+
+        var returnedSigningRequestDocument = Instancio.of(SigningRequestDocument.class)
+                .set(field(SigningRequestDocument::isConfirmed), false)
+                .create();
+        when(signingRequestDocumentService.getSigningRequestDocument(id.toString()))
+                .thenReturn(returnedSigningRequestDocument);
+
+        signingRequestDocumentController.patchSigningRequestDocument(id.toString(), patchOperations);
+
+        var documentCaptor = ArgumentCaptor.forClass(SigningRequestDocument.class);
+        verify(signingRequestDocumentService).updateSigningRequestDocument(documentCaptor.capture());
+
+        assertTrue(documentCaptor.getValue().isConfirmed());
+    }
+
+    @Test
+    public void givenNonExistingSigningRequestDocument_whenPatchSigningRequestDocument_thenThrowNoSuchElementException() {
+        var id = UUID.randomUUID();
+        var patchOperations = List.of(
+                new PatchOperation("replace", "/confirmed", "true")
+        );
+
+        when(signingRequestDocumentService.getSigningRequestDocument(id.toString()))
+                .thenThrow(NoSuchElementException.class);
+
+        assertThrows(NoSuchElementException.class, () -> {
+            signingRequestDocumentController.patchSigningRequestDocument(id.toString(), patchOperations);
+        });
+    }
+
+    @Test
+    public void givenInvalidPatchOperationPath_whenPatchSigningRequestDocument_thenThrowIllegalArgumentException() {
+        var id = UUID.randomUUID();
+        var patchOperations = List.of(
+                new PatchOperation("replace", "/invalid", "true")
+        );
+
+        var returnedSigningRequestDocument = Instancio.of(SigningRequestDocument.class)
+                .set(field(SigningRequestDocument::isConfirmed), false)
+                .create();
+        when(signingRequestDocumentService.getSigningRequestDocument(id.toString()))
+                .thenReturn(returnedSigningRequestDocument);
+
+        assertThrows(IllegalArgumentException.class, () -> {
+            signingRequestDocumentController.patchSigningRequestDocument(id.toString(), patchOperations);
+        });
+    }
+
+    @Test
+    public void givenInvalidPatchOperationValue_whenPatchSigningRequestDocument_thenThrowIllegalArgumentException() {
+        var id = UUID.randomUUID();
+        var patchOperations = List.of(
+                new PatchOperation("replace", "/confirmed", "notabool")
+        );
+
+        var returnedSigningRequestDocument = Instancio.of(SigningRequestDocument.class)
+                .set(field(SigningRequestDocument::isConfirmed), false)
+                .create();
+        when(signingRequestDocumentService.getSigningRequestDocument(id.toString()))
+                .thenReturn(returnedSigningRequestDocument);
+
+        assertThrows(IllegalArgumentException.class, () -> {
+            signingRequestDocumentController.patchSigningRequestDocument(id.toString(), patchOperations);
+        });
+    }
+}