Symbolic Calls
Explore symbolic calls to improve custom data generators in property-based testing using PropEr. Understand how representing function calls as data structures aids in debugging complex states and opaque data, making test failures easier to interpret and analyze.
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What are symbolic calls?
Some of the data structures or states that we need to generate for tests can be opaque and difficult to decipher. Think of debugging a binary protocol by looking at the individual bytes once the whole thing is encoded, or creating a process and sending it a bunch of messages to prime its state. The output of a failing property will be a lot of hard-to-read bits and bytes, or a term like <0.213.0>, which is not very helpful regardless of how much shrinking we may apply to them. The solution to this problem is a special category of generators built from symbolic calls.
A symbolic call is just a special notation for function calls so that they can be represented as data in generators. Rather than executing ...