Gremlin said today it has raised $18 million as the company expanded its product lineup to offer additional ways for companies to stress-test their applications.

The round was led by Redpoint Ventures. Founded in 2016 by a pair of former engineers from Amazon and Netflix, the company has been designing ways for companies to test their systems by simulating moments when they are hit with surges in traffic to identify weaknesses.

As part of today’s announcement, the company also introduced a new service called¬†Application Level Fault Injection, or ALFI. The service allows a company to deliberately cause part of its systems to fail to see how the rest of the system reacts, and ideally fix any weaknesses that are identified.

“The concept of purposefully injecting harm into systems is still new for many companies, but chaos engineering has been practiced at places like Amazon and Netflix for over a decade,” said Kolton Andrus, CEO and cofounder of Gremlin, in a statement. “We like to use the analogy of a flu shot, injecting small amounts of harm to build an immunity, in order to proactively avoid disasters. Now with ALFI, users will be able to bring this practice to serverless environments, and have much greater control within their applications.”

With more and more companies migrating their services online, customers have come to expect zero downtime and increased reliability. But the unwieldy patchwork of systems, software, and architectures can lead to vulnerabilities that are hard to spot through routine checks.

“With ALFI one of the first problems we wanted to address was improving the reliability and understanding of serverless providers like AWS Lambda and Azure Functions,” said Matthew Fornaciari, CTO and cofounder of Gremlin, in a statement.

Gremlin has now raised $23.75 million in total funding. Investors include Redpoint Ventures, Index Ventures, and Amplify Ventures.