solid_assert

solid_assert is a simple implementation of an assert utility in Ruby. It let you code tests for your assumptions inside your code itself.

Assertions are meant to test conditions about the integrity of your code. You should use them for testing assumptions like the following:

• If the flow reaches here, then this variable has to have this value.
• This line of code should never be executed.
• At this point, this list should contain one entry for all the keys in this hash.

Notice that assertions shouldn't be used for handling error situations. Use Ruby built-in exception handling for that.

Assertions are typically used in development mode. You might want to disable them in production for performance reasons.

Installation

In your Gemfile

gem "solid_assert"

Usage

You can enable assertions with

SolidAssert.enable_assertions

Assertions are disabled by default.

Use assert for testing conditions. You can optionally provide a message

assert some_string != "some value"
assert clients.empty?, "Isn't the clients list empty?"

Use invariant for testing blocks of code. This comes handy when testing your assumptions requires several lines of code. You can provide an optional message if you want

invariant do
    one_variable = calculate_some_value
    other_variable = calculate_some_other_value
    one_variable > other_variable
end

invariant "Have the lists had different sizes?" do
    one_variable = calculate_some_value
    other_variable = calculate_some_other_value
    one_variable > other_variable
end

References

• Programming with assertions. A great article on assertions. It is about the Java language, but the concepts it explains apply to any programming language.
• Writing Solid Code. A great book on good coding design practices. Again, it based in C, but the practices it talks about apply to coding in any programming language.