What do series values stand for in Prometheus unit test? - unit-testing

Question

I am trying to understand what series values stand for in Prometheus unit test.
The official doc does not provide any info.
For example, fire an alert if any instance is down over 10 seconds.
alerting-rules.yml
groups:
- name: alert_rules
rules:
- alert: InstanceDown
expr: up == 0
for: 10s
labels:
severity: critical
annotations:
summary: "Instance {{ $labels.instance }} down"
description: "{{ $labels.instance }} of job {{ $labels.job }} has been down for more than 10 seconds."
alerting-rules.test.yml
rule_files:
- alerting-rules.yml
evaluation_interval: 1m
tests:
- interval: 1m
input_series:
- series: 'up{job="prometheus", instance="localhost:9090"}'
values: '0 0 0 0 0 0 0 0 0 0 0 0 0 0 0'
alert_rule_test:
- eval_time: 10m
alertname: InstanceDown
exp_alerts:
- exp_labels:
severity: critical
instance: localhost:9090
job: prometheus
exp_annotations:
summary: "Instance localhost:9090 down"
description: "localhost:9090 of job prometheus has been down for more than 10 seconds."
Originally, I thought because of interval: 1m, which is 60 seconds, and there are 15 numbers, 60 / 15 = 4s, so each value stands for 4 seconds (1 means up, 0 means down).
However, when the values are
values: '0 0 0 0 0 0 0 0 0 0 0 0 0 0 0'
or
values: '1 1 1 1 1 1 1 1 1 0 0 0 0 0 0'
Both will pass the test when I run promtool test rules alerting-rules.test.yml.
But below will fail:
values: '1 1 1 1 1 1 1 1 1 1 0 0 0 0 0'
So my original thought each number stands for 4s is wrong. If my assumption is correct, then only when less three 0s will fail the test.
What do series values stand for in Prometheus unit test?

Answer 1

Your assumption is incorrrect. The number in the values doesn't correspond at the number of value in the interval but which value the series will have after each interval. For example:
values: 1 1 1 1 1 1
# 1m 2m 3m 4m 5m 6m
In your example, since you evaluate the value at 10min (with eval_time) the evaluation will be based on the tenth value in the values. Since you check if up==0, when you change the tenth value to 1 it will fail because the alert will not be trigger as excepted.