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prometheus/promql/promqltest/README.md

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# The PromQL test scripting language
This package contains two things:
* an implementation of a test scripting language for PromQL engines
* a predefined set of tests written in that scripting language
The predefined set of tests can be run against any PromQL engine implementation by calling `promqltest.RunBuiltinTests()`.
Any other test script can be run with `promqltest.RunTest()`.
The rest of this document explains the test scripting language.
Each test script is written in plain text.
Comments can be given by prefixing the comment with a `#`, for example:
```
# This is a comment.
```
Each test file contains a series of commands. There are three kinds of commands:
* `load`
* `clear`
* `eval`
Each command is executed in the order given in the file.
## `load` command
`load` adds some data to the test environment.
The syntax is as follows:
```
load <interval>
<series> <points>
...
<series> <points>
```
* `<interval>` is the step between points (eg. `1m` or `30s`)
* `<series>` is a Prometheus series name in the usual `metric{label="value"}` syntax
* `<points>` is a specification of the points to add for that series, following the same expanding syntax as for `promtool unittest` documented [here](../../docs/configuration/unit_testing_rules.md#series)
For example:
```
load 1m
my_metric{env="prod"} 5 2+3x2 _ stale {{schema:1 sum:3 count:22 buckets:[5 10 7]}}
```
...will create a single series with labels `my_metric{env="prod"}`, with the following points:
* t=0: value is 5
* t=1m: value is 2
* t=2m: value is 5
* t=3m: value is 7
* t=4m: no point
* t=5m: stale marker
* t=6m: native histogram with schema 1, sum -3, count 22 and bucket counts 5, 10 and 7
Each `load` command is additive - it does not replace any data loaded in a previous `load` command.
Use `clear` to remove all loaded data.
### Native histograms with custom buckets (NHCB)
When loading a batch of classic histogram float series, you can optionally append the suffix `_with_nhcb` to convert them to native histograms with custom buckets and load both the original float series and the new histogram series.
## `clear` command
`clear` removes all data previously loaded with `load` commands.
## `eval` command
`eval` runs a query against the test environment and asserts that the result is as expected.
Both instant and range queries are supported.
The syntax is as follows:
```
# Instant query
eval instant at <time> <query>
<series> <points>
...
<series> <points>
# Range query
eval range from <start> to <end> step <step> <query>
<series> <points>
...
<series> <points>
```
* `<time>` is the timestamp to evaluate the instant query at (eg. `1m`)
* `<start>` and `<end>` specify the time range of the range query, and use the same syntax as `<time>`
* `<step>` is the step of the range query, and uses the same syntax as `<time>` (eg. `30s`)
* `<series>` and `<points>` specify the expected values, and follow the same syntax as for `load` above
For example:
```
eval instant at 1m sum by (env) (my_metric)
{env="prod"} 5
{env="test"} 20
eval range from 0 to 3m step 1m sum by (env) (my_metric)
{env="prod"} 2 5 10 20
{env="test"} 10 20 30 45
```
Instant queries also support asserting that the series are returned in exactly the order specified: use `eval_ordered instant ...` instead of `eval instant ...`.
This is not supported for range queries.
It is also possible to test that queries fail: use `eval_fail instant ...` or `eval_fail range ...`.
`eval_fail` optionally takes an expected error message string or regexp to assert that the error message is as expected.
For example:
```
# Assert that the query fails for any reason without asserting on the error message.
eval_fail instant at 1m ceil({__name__=~'testmetric1|testmetric2'})
# Assert that the query fails with exactly the provided error message string.
eval_fail instant at 1m ceil({__name__=~'testmetric1|testmetric2'})
expected_fail_message vector cannot contain metrics with the same labelset
# Assert that the query fails with an error message matching the regexp provided.
eval_fail instant at 1m ceil({__name__=~'testmetric1|testmetric2'})
expected_fail_regexp (vector cannot contain metrics .*|something else went wrong)
```