Feature/testing contributing doc (#197)

docs/POLICY_RULES.md

@@ -0,0 +1,78 @@
+
+# API rules validation
+
+This feature allows you to define set of simple rules, and test the API against them.
+Such validation may test response for specific JSON fields, headers, etc.
+
+## Examples
+
+
+Example 1: HTTP request (REST API call) that didn’t pass validation is highlighted in red
+
+![Simple UI](../assets/validation-example1.png)
+
+- - -
+
+
+Example 2: Details pane shows the validation rule details and whether it passed or failed
+
+![Simple UI](../assets/validation-example2.png)
+
+
+## How to use
+To use this feature - create simple rules file (see details below) and pass this file as parameter to `mizu tap` command. For example, if rules are stored in file named `rules.yaml` — run the following command:
+
+
+```shell
+mizu tap --test-rules rules.yaml PODNAME
+```
+
+
+
+## Rules file structure
+
+The structure of the test-rules-file is:
+
+* `name`: string, name of the rule
+* `type`: string, type of the rule, must be `json` or `header` or `latency`
+* `key`: string, [jsonpath](https://code.google.com/archive/p/jsonpath/wikis/Javascript.wiki) used only in `json` or `header` type
+* `value`: string, [regex](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions) used only in `json` or `header` type
+* `service`: string, [regex](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions) service name to filter
+* `path`: string, [regex](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions) URL path to filter
+* `latency`: integer, time in ms of the expected latency.
+
+
+### For example:
+
+```yaml
+rules:
+- name: holy-in-name-property
+  type: json
+  key: "$.name"
+  value: "Holy"
+  service: "catalogue.*"
+  path: "catalogue.*"
+- name: content-length-header
+  type: header
+  key: "Content-Le.*"
+  value: "(\\d+(?:\\.\\d+)?)"
+- name: latency-test
+  type: latency
+  latency: 1
+  service: "carts.*"
+```
+
+### Explanation:
+
+* First rule `holy-in-name-property`:
+
+  > This rule will be applied to all request made to `catalogue.*` services with `catalogue.*` on the URL path with a json response containing a `$.name` field. If the value of `$.name` is `Holy` than is marked as success, marked as failure otherwise.
+
+* Second rule `content-length-header`:
+
+  > This rule will be applied to all request that has `Content-Le.*` on header. If the value of `Content-Le.*` is `(\\d+(?:\\.\\d+)?)` (number), will be marked as success, marked as failure otherwise.
+
+* Third rule `latency-test`:
+
+  > This rule will be applied to all request made to `carts.*` services. If the latency of the response is greater than `1` will be marked as failure, marked as success otherwise.
+