> ## Properties and Assertions

> Properties and assertions overview. Express how your system should behave with assertions instead of example-based tests.

> Fetch the complete documentation index at: https://antithesis.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

---

Even if you're unfamiliar with the concept of software properties, you're already using them to reason about your software -- because you know what your system *ought* to do.

Should your software crash? That's a property. Should your system run out of memory? That's another.
Should your database return the latest write? That's a property too.

Traditional software testing involves writing a vast test harness that *hopefully* ensures your system has the properties promised in your documentation or system spec. But it does this in a roundabout way -- by checking a large number of pre-written cases which together embody the properties you care about. If you're *very lucky,* your tests include the right number and right kind of cases to ensure that your properties always hold.

Antithesis takes a different approach: **property-based testing**. You *directly state* how your system ought to behave -- that it should have certain properties -- and Antithesis runs your system in a multitude of situations to see if they're ever violated. You express these properties by including **assertions** in your software [using our SDKs](/docs/reference/sdk/) (similar to the programming assertions you might have used).

There are significant advantages to this approach, which we outline in [How Antithesis Works](/docs/introduction/how_antithesis_works/). In this section, we explain how the platform handles properties and assertions, to build your mental model of how to test your software in Antithesis.

In this section:

- [Properties in Antithesis](/docs/concepts/properties_assertions/properties/)
- [Assertions in Antithesis](/docs/concepts/properties_assertions/assertions/)
- [Sometimes Assertions](/docs/concepts/properties_assertions/sometimes_assertions/)
- [Properties to test for](/docs/concepts/properties_assertions/reliability_properties/)

Language-specific references:

- [Go Assertions](https://antithesis.com/docs/generated/sdk/golang/assert/)
- [Java Assertions](https://antithesis.com/docs/generated/sdk/java/com/antithesis/sdk/Assert.html)
- [C++ Assertions](/docs/reference/sdk/cpp/assert/)
- [Python Assertions](https://antithesis.com/docs/generated/sdk/python/antithesis/assertions.html)
- [Rust Assertions](https://antithesis.com/docs/generated/sdk/rust/antithesis_sdk/assert/)
- [Languages not listed above](/docs/reference/sdk/fallback/assert/)