---
title: "TAP Tests"
id: regress-tap
pg_version: "20devel"
---

<a id="regress-tap"></a>

## 31.4. TAP Tests

Various tests, particularly the client program tests under `src/bin`, use the Perl TAP tools and are run using the Perl testing program `prove`. You can pass command-line options to `prove` by setting the `make` variable `PROVE_FLAGS`, for example: 
make -C src/bin check PROVE_FLAGS='--timer'
 See the manual page of `prove` for more information. 

The `make` variable `PROVE_TESTS` can be used to define a whitespace-separated list of paths relative to the `Makefile` invoking `prove` to run the specified subset of tests instead of the default `t/*.pl`. For example: 
make check PROVE_TESTS='t/001_test1.pl t/003_test3.pl'
 

The TAP tests require the Perl module `IPC::Run`. This module is available from [CPAN](https://metacpan.org/dist/IPC-Run) or an operating system package. They also require PostgreSQL to be configured with the option `--enable-tap-tests`. 

Generically speaking, the TAP tests will test the executables in a previously-installed installation tree if you say `make installcheck`, or will build a new local installation tree from current sources if you say `make check`. In either case they will initialize a local instance (data directory) and transiently run a server in it. Some of these tests run more than one server. Thus, these tests can be fairly resource-intensive. 

It's important to realize that the TAP tests will start test server(s) even when you say `make installcheck`; this is unlike the traditional non-TAP testing infrastructure, which expects to use an already-running test server in that case. Some PostgreSQL subdirectories contain both traditional-style and TAP-style tests, meaning that `make installcheck` will produce a mix of results from temporary servers and the already-running test server. 

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### 31.4.1. Environment Variables

Data directories are named according to the test filename, and will be retained if a test fails. If the environment variable `PG_TEST_NOCLEAN` is set, data directories will be retained regardless of test status. For example, retaining the data directory regardless of test results when running the pg_dump tests: 
PG_TEST_NOCLEAN=1 make -C src/bin/pg_dump check
 This environment variable also prevents the test's temporary directories from being removed. 

Many operations in the test suites use a 180-second timeout, which on slow hosts may lead to load-induced timeouts. Setting the environment variable `PG_TEST_TIMEOUT_DEFAULT` to a higher number will change the default to avoid this. 

For certain tests, the environment variable PG_TEST_FILE_READ_LINES can be set to limit the number of lines read from large output files (head and tail). This is useful when the test output contains a lot of unnecessary content, allowing the test framework to read only a limited number of lines for its reports.