diff --git a/src/darwin/Framework/CHIPTests/TestHelpers/MTRTestKeys.h b/src/darwin/Framework/CHIPTests/TestHelpers/MTRTestKeys.h
index 8741eb584e3572..9afe75266d1eed 100644
--- a/src/darwin/Framework/CHIPTests/TestHelpers/MTRTestKeys.h
+++ b/src/darwin/Framework/CHIPTests/TestHelpers/MTRTestKeys.h
@@ -25,6 +25,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (readonly, nonatomic) NSData * publicKeyData;
 
+// Count of how many times this keypair has been used to signMessageECDSA_DER.
+@property (readonly, nonatomic, assign) unsigned signatureCount;
+
 - (instancetype)init;
 
 @end
diff --git a/src/darwin/Framework/CHIPTests/TestHelpers/MTRTestKeys.m b/src/darwin/Framework/CHIPTests/TestHelpers/MTRTestKeys.m
index 2d073f64d11fb4..23b602e2e7208c 100644
--- a/src/darwin/Framework/CHIPTests/TestHelpers/MTRTestKeys.m
+++ b/src/darwin/Framework/CHIPTests/TestHelpers/MTRTestKeys.m
@@ -69,11 +69,15 @@ - (instancetype)init
     }
     _publicKey = SecKeyCopyPublicKey(_privateKey);
 
+    _signatureCount = 0;
+
     return self;
 }
 
 - (NSData *)signMessageECDSA_DER:(NSData *)message
 {
+    ++_signatureCount;
+
     CFErrorRef error = NULL;
     CFDataRef outData
         = SecKeyCreateSignature(_privateKey, kSecKeyAlgorithmECDSASignatureMessageX962SHA256, (__bridge CFDataRef) message, &error);