n8n Custom Node Credential Test Fails Due to Internal Loader Bug, Fix Available

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Developers building custom n8n nodes have long encountered a 'No testing function found for this credential' error when clicking the Test button in the UI, even with credentialTest correctly defined. The root cause lies in n8n's LoadNodesAndCredentials.ts, where the loader checks supportedNodes but generates nodesToTestWith, meaning the credential-to-test linkage silently breaks for custom and community nodes. The bug, tracked as n8n-io/n8n#8188 and originally reported on Stack Overflow, continues to affect users on versions as recent as 1.94 despite an earlier official fix. The recommended solution is to move the test logic directly onto the credential class as an ICredentialTestRequest object, eliminating any dependency on the node-side credentialTest method. This self-contained approach works regardless of whether the node is symlinked into ~/.n8n/custom or installed as a packaged module.

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