Fix docs (#4690)

Signed-off-by: Ganesh Vernekar <cs15btech11018@iith.ac.in>

docs/configuration/unit_testing_rules.md

@@ -133,35 +133,9 @@ value: <number>
 
 ## Example 
 
-This is an example input files for unit testing which passes the test. `alerts.yml` contains the alerting rule, `tests.yml` is the test file which follows the syntax above.
+This is an example input file for unit testing which passes the test. `test.yml` is the test file which follows the syntax above and `alerts.yml` contains the alerting rules.
 
-### `alerts.yml`
-
-```yaml
-# This is the rules file.
-
-groups:
-- name: example
-  rules:
-
-  - alert: InstanceDown
-    expr: up == 0
-    for: 5m
-    labels:
-        severity: page
-    annotations:
-        summary: "Instance {{ $labels.instance }} down"
-        description: "{{ $labels.instance }} of job {{ $labels.job }} has been down for more than 5 minutes."
-
-  - alert: AnotherInstanceDown
-    expr: up == 0
-    for: 10m
-    labels:
-        severity: page
-    annotations:
-        summary: "Instance {{ $labels.instance }} down"
-        description: "{{ $labels.instance }} of job {{ $labels.job }} has been down for more than 5 minutes."
-```
+With `alerts.yml` in the same directory, run `./promtool test rules test.yml`.
 
 ### `test.yml`
 
@@ -215,3 +189,31 @@ tests:
                 - labels: 'go_goroutines{job="node_exporter",instance="localhost:9100"}'
                   value: 50
 ```
+
+### `alerts.yml`
+
+```yaml
+# This is the rules file.
+
+groups:
+- name: example
+  rules:
+
+  - alert: InstanceDown
+    expr: up == 0
+    for: 5m
+    labels:
+        severity: page
+    annotations:
+        summary: "Instance {{ $labels.instance }} down"
+        description: "{{ $labels.instance }} of job {{ $labels.job }} has been down for more than 5 minutes."
+
+  - alert: AnotherInstanceDown
+    expr: up == 0
+    for: 10m
+    labels:
+        severity: page
+    annotations:
+        summary: "Instance {{ $labels.instance }} down"
+        description: "{{ $labels.instance }} of job {{ $labels.job }} has been down for more than 5 minutes."
+```