# Reactis Validator

```{epigraph}
The verification and validation capabilities of Reactis for C help
engineers detect bugs earlier, when they are less costly to fix.
```

Reactis Validator automatically searches C programs for violations of
user-specified requirements. When a violation is discovered by Reactis
Validator, a test which triggers the violation is produced. This test can
then be executed in Reactis Simulator to gain an understanding of the
sequence of events that leads to the violation. Validator helps detect
defects early in the software life-cycle and reduces the effort required
for code reviews. Some checks that may be performed with Validator include
the following:

* Will a particular program variable ever fall outside a specified range?

* Will a thermostat maintain ambient temperature within acceptable limits
  of the desired temperature?

* Will engaging a vehicle's brake pedal always override the electronic
  throttle control?

* Will a radiation therapy machine ever deliver a dangerous dose of
  radiation?

* Will anti-lock brakes disengage whenever a vehicle begins to skid?

{numref}`Figure {number}<reactis-for-c-validator-fig>` illustrates how
Validator is used. First, a program is instrumented with Validator
objectives. There are two kinds of Validator objectives, assertions and
user-defined coverage targets. An assertion is a boolean C function which
should always return a true (i.e., non-zero) value. A user-defined coverage
target is a boolean C function which should return a true result at least
once during the test process. The actual instrumentation process involves
inserting reactis_assert and reactis_target statements into your code. The
purpose of Validator is to take a program and a set of objectives and
produce a test suite which triggers assertion violations and covers all
user-defined coverage targets.

```{figure} images/reactis-for-c-validator.png
---
width: 65%
name: reactis-for-c-validator-fig
---
Reactis Validator automates functional testing.
```

Once the program has been instrumented, Reactis Validator performs an
automated search for a sequence of input values which, when executed, leads
to the violation of an assertion. Whenever an assertion violation is found,
Validator produces a test that triggers the violation. This test may then
be used within the interactive execution environment of Reactis Simulator
in order to understand the sequence of events which causes the problem.

Reactis Validator makes it possible to detect software defects prior to
code release with less effort, which in turn reduces overall development
costs.