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https://github.com/anderseknert/rego-test-assertions

Tiny Rego library with helper functions for unit testing
https://github.com/anderseknert/rego-test-assertions

assertions assertions-library opa open-policy-agent policy policy-as-code rego testing

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Tiny Rego library with helper functions for unit testing

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# rego-test-assertions



Tiny [Rego](https://www.openpolicyagent.org/docs/latest/policy-language/) library providing helper

functions for unit testing. The library primarily contains various assertion functions, which will

[print](https://blog.openpolicyagent.org/introducing-the-opa-print-function-809da6a13aee)

the expected result vs. the outcome to the console on failure. This allows you to quickly grasp

what went wrong in your unit tests, resulting in a faster test iteration process!



> This assert library is what I’ve been wanting since I started using OPA.

> Fixed something in ten minutes, while eating a sandwich, I’d previously been poking at for a couple of hours.

> You’ve made my day!



— Duncan Thomas, Groupon



## Usage



Simply download the test assertions library

[policy file](https://raw.githubusercontent.com/anderseknert/rego-test-assertions/main/test/assert.rego)

and place it somewhere `opa test` checks for policy and tests:



Alternatively, use [ODM](https://github.com/johanfylling/opa-dependency-manager) to add the library to your project:



```shell

odm depend rego-test-assertions --no-namespace \

    git+https://github.com/anderseknert/rego-test-assertions

```



In order to use the test assertion functions, import the `test.assert` package:



```rego

import data.test.assert

```



## Functions



Once imported, all functions may now be referenced like `assert.`. Using the assert package prefix avoids

having these functions clash with other built-ins and custom functions, and makes it clear in your test code what

the purpose of these functions is. As an added bonus, you won't need repeated import statements to import each

function separetely.



| Function                   | Arguments            | Example console output                                   |

|----------------------------|----------------------|----------------------------------------------------------|

| `assert.equals`            | `expected`, `result` | expected equals: "foo" got: "bar"                        |

| `assert.not_equals`        | `expected`, `result` | expected not equals: 1 got: 1                            |

| `assert.all_equals`        | `coll`, `value`      | expected all items to have value 2, failed for [1]       |

| `assert.none_equals`       | `coll`, `value`      | expected no items to have value 2, failed for [2, 2]     |

| `assert.has`               | `item`, `coll`       | expected string "foo" in array got: ["bar", "baz"]       |

| `assert.not_has`           | `item`, `coll`       | expected string "foo" not in set got {"foo", "x"}        |

| `assert.empty`             | `coll`               | expected empty set got: {"admin", "dba"}                 |

| `assert.not_empty`         | `coll`               | expected empty array                                     |

| `assert.starts_with`       | `str`, `search`      | expected "test" to start with "a"                        |

| `assert.ends_with`         | `str`, `search`      | expected "test" to end with "a"                          |

| `assert.all_starts_with`   | `coll`, `search`     | expected all strings to start with "a", failed for ["b"] |

| `assert.all_ends_with`     | `coll`, `search`     | expected all strings to end with "a", failed for ["b"]   |

| `assert.none_starts_swith` | `coll`, `search`     | expected no strings to start with "a", failed for ["a"]  |

| `assert.none_ends_swith`   | `coll`, `search`     | expected no strings to end with "a", failed for ["a"]    |

| `assert.fail`              | `msg`                | fail with provided message!                              |



## Example



### Policy



```rego

package rego.example



deny[msg] {

    msg := "I'll always deny that"

}



violation[msg] {

    input.user.name == "banned"

    msg := "You're banned!"

}

```



### Test without assertions



```rego

package rego.example_test



import future.keywords.in



import data.example.deny

import data.example.violation



test_empty_without_assertion {

    count(deny) == 0

}



test_in_without_assertion {

    "You're banned!" in violation with input.user.name as "bob"

}

```



```shell

❯ opa test example_test.rego

example_test.rego:

data.rego.example_test.test_empty_without_assertion: FAIL (178.375µs)

data.rego.example_test.test_in_without_assertion: FAIL (99.416µs)



--------------------------------------------------------------------------------

FAIL: 2/2

```



### Test with assertions



```rego

package rego.example_test



import data.example.deny

import data.example.violation



import data.test.assert



test_empty_with_assertion {

    assert.empty(deny)

}



test_in_with_assertion {

    assert.has("You're banned!", violation) with input.user.name as "bob"

}

```



```shell

❯ opa test example_test.rego

example_test.rego:

data.rego.example_test.test_empty_with_assertion: FAIL (206.5µs)



  expected empty set got {"I'll always deny that"}



data.rego.example_test.test_in_with_assertion: FAIL (138.792µs)



  expected string "You're banned!" in set got set()



--------------------------------------------------------------------------------

FAIL: 2/2

```



## Prerequisites



OPA v0.39.0 and above — a [bug](https://github.com/open-policy-agent/opa/issues/4489) in older versions caused

the `print` function to error in `else` blocks, which this library makes heavy use of.