diff --git a/src/test/java/com/vonage/client/subaccounts/CreateSubaccountRequestTest.java b/src/test/java/com/vonage/client/subaccounts/CreateSubaccountRequestTest.java
index 409adaee5..c33d82800 100644
--- a/src/test/java/com/vonage/client/subaccounts/CreateSubaccountRequestTest.java
+++ b/src/test/java/com/vonage/client/subaccounts/CreateSubaccountRequestTest.java
@@ -54,9 +54,13 @@ public void testConstructNoName() {
 	}
 
 	@Test
-	public void testConstructShortSecret() {
+	public void testConstructSecretLength() {
 		CreateSubaccountRequest.Builder builder = CreateSubaccountRequest.builder().name("Department C");
-		assertThrows(IllegalArgumentException.class, () -> builder.secret("A1b23c5").build());
+		String min = "*A1b23c5", max = "A1b2*".repeat(5);
+		assertEquals(min, builder.secret(min).build().getSecret());
+		assertEquals(max, builder.secret(max).build().getSecret());
+		assertThrows(IllegalArgumentException.class, () -> builder.secret(min.substring(1)).build());
+		assertThrows(IllegalArgumentException.class, () -> builder.secret(max + "T").build());
 	}
 
 	@Test
diff --git a/src/test/java/com/vonage/client/subaccounts/SubaccountsClientTest.java b/src/test/java/com/vonage/client/subaccounts/SubaccountsClientTest.java
index 5452c73c3..a7f9a3635 100644
--- a/src/test/java/com/vonage/client/subaccounts/SubaccountsClientTest.java
+++ b/src/test/java/com/vonage/client/subaccounts/SubaccountsClientTest.java
@@ -326,6 +326,7 @@ public void testListCreditTransfers() throws Exception {
 		assertNotNull(response.get(2));
 		assertEqualsExpectedMoneyTransfer(response.get(1));
 		assertNotNull(stubResponseAndGet(responseJson, client::listCreditTransfers));
+		assertNull(stubResponseAndGet("{}", client::listCreditTransfers));
 		stubResponseAndAssertThrows(200, () -> client.listCreditTransfers(null), NullPointerException.class);
 		stubResponseAndAssertThrows(401, () -> client.listCreditTransfers(request), SubaccountsResponseException.class);
 		assert403ResponseException(client::listCreditTransfers);
@@ -370,6 +371,7 @@ public void testListBalanceTransfers() throws Exception {
 		assertNotNull(response.get(2));
 		assertEqualsExpectedMoneyTransfer(response.get(1));
 		assertNotNull(stubResponseAndGet(responseJson, client::listBalanceTransfers));
+		assertNull(stubResponseAndGet("{}", client::listBalanceTransfers));
 		stubResponseAndAssertThrows(200, () -> client.listBalanceTransfers(null), NullPointerException.class);
 		stubResponseAndAssertThrows(401, () -> client.listBalanceTransfers(request), SubaccountsResponseException.class);
 		assert403ResponseException(client::listBalanceTransfers);
@@ -513,6 +515,9 @@ public void testTransferNumber() throws Exception {
 				.from(request.getFrom()).to(request.getTo()).number(request.getNumber())
 				.country("United Kingdom").build()
 		);
+		assertThrows(IllegalArgumentException.class, () -> NumberTransfer.builder()
+				.from(request.getFrom()).to(request.getTo()).number(request.getNumber()).build()
+		);
 
 		new SubaccountsEndpointTestSpec<NumberTransfer, NumberTransfer>() {
 
diff --git a/src/test/java/com/vonage/client/subaccounts/UpdateSubaccountRequestTest.java b/src/test/java/com/vonage/client/subaccounts/UpdateSubaccountRequestTest.java
index 01886bfe4..3b00c24ef 100644
--- a/src/test/java/com/vonage/client/subaccounts/UpdateSubaccountRequestTest.java
+++ b/src/test/java/com/vonage/client/subaccounts/UpdateSubaccountRequestTest.java
@@ -38,9 +38,11 @@ public void testSerializeAllParameters() {
 
 	@Test
 	public void testSerializeRequiredParameters() {
-		UpdateSubaccountRequest.Builder builder  = UpdateSubaccountRequest.builder("abc6123f");
+		var builder = UpdateSubaccountRequest.builder("abc6123f");
 		assertThrows(IllegalStateException.class, builder::build);
 		assertEquals("{\"suspended\":false}", builder.suspended(false).build().toJson());
+		builder.usePrimaryAccountBalance(true);
+		assertEquals("{\"use_primary_account_balance\":true,\"suspended\":false}", builder.build().toJson());
 	}
 
 	@Test