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IntelliTest (formerly Smart Unit Tests)

2 posts · Nov 2014 – Dec 2014

What this trail covers

This thread tracks the evolution of automated unit test generation and analysis. Initially introduced as 'Smart Unit Tests', this capability, now named 'IntelliTest', uses runtime instrumentation and monitoring to generate compact test suites with high code coverage. It employs constraint solving to synthesize new input values that explore uncovered branches and potential bugs. The system relies on assertions to connect code coverage with correctness, effectively identifying bugs when assertions are falsified. This post details the initial release of Smart Unit Tests, highlighting its ability to discover code paths, synthesize test inputs, and record observed behavior as a baseline regression suite, or to validate user-defined assertions.

All Microsoft trails
  1. Smart Unit Tests - a mental modelThis post introduces the mental model and technical details behind 'Smart Unit Tests' (renamed to 'IntelliTest'). It explains the core mechanism of runtime instrumentation, monitoring, and constraint solving to generate unit tests. The process involves instrumenting code, running it with simple inputs, monitoring execution and coverage, identifying uncovered branches, constructing constraint systems for those branches, querying a constraint solver for new inputs, and emitting test cases only when coverage increases. It also highlights the role of assertions in bug detection.
  2. Introducing Smart Unit TestsIntroduces the Smart Unit Tests feature (later renamed IntelliTest) which automatically discovers code paths in a given piece of code, synthesizes precise test input values that exercise those code paths, and records the output. It persists these as a compact test suite with high coverage. By default, it captures observed behavior, useful as a regression suite. It can also validate user-defined assertions to identify bugs.