Acceptance criteria for the lib/runcmd Subplot library
The Subplot project
2022-04-10 09:02
1 Introduction
The Subplot library runcmd for Python provides scenario steps and their implementations for running Unix commands and examining the results. The library consists of a bindings file lib/runcmd.yaml and implementations in Python in lib/runcmd.py or in the Rust subplotlib step library. There is no Bash version.
This document explains the acceptance criteria for the library and how they’re verified. It uses the steps and functions from the lib/runcmd library. The scenarios all have the same structure: run a command, then examine the exit code, standard output (stdout for short), or standard error output (stderr) of the command.
The scenarios use the Unix commands true and false to generate exit codes, and echo to produce stdout. To generate stderr, they use the little helper script below.
File: err.sh
#!/bin/shecho"$@"1>&2
2 Check exit code
These scenarios verify the exit code. To make it easier to write scenarios in language that flows more naturally, there are a couple of variations.
2.1 Successful execution
when I run true then exit code is 0 and command is successful
2.2 Successful execution in a sub-directory
given a directory xyzzy when I run, in xyzzy, pwd then exit code is 0 and command is successful and stdout contains "/xyzzy"
2.3 Failed execution
when I try to run false then exit code is not 0 and command fails
2.4 Failed execution in a sub-directory
given a directory xyzzy when I try to run, in xyzzy, false then exit code is not 0 and command fails
3 Check we can prepend to $PATH
This scenario verifies that we can add a directory to the beginning of the PATH environment variable, so that we can have runcmd invoke a binary from our build tree rather than from system directories. This is especially useful for testing new versions of software that’s already installed on the system.
given executable script ls from ls.sh when I prepend . to PATH and I run ls then command is successful and stdout contains "custom ls, not system ls"
File: ls.sh
#!/bin/shecho"custom ls, not system ls"
4 Check output has what we want
These scenarios verify that stdout or stderr do have something we want to have.
4.1 Check stdout is exactly as wanted
Note that the string is surrounded by double quotes to make it clear to the reader what’s inside. Also, C-style string escapes are understood.
when I run echo hello, world then stdout is exactly "hello, world\n"
4.2 Check stderr is exactly as wanted
given helper script err.sh for runcmd when I run sh err.sh hello, world then stderr is exactly "hello, world\n"
4.3 Check stdout using sub-string search
Exact string comparisons are not always enough, so we can verify a sub-string is in output.
when I run echo hello, world then stdout contains "world\n" and exit code is 0
4.4 Check stderr using sub-string search
given helper script err.sh for runcmd when I run sh err.sh hello, world then stderr contains "world\n"
4.5 Check stdout using regular expressions
Fixed strings are not always enough, so we can verify output matches a regular expression. Note that the regular expression is not delimited and does not get any C-style string escaped decoded.
when I run echo hello, world then stdout matches regex world$
4.6 Check stderr using regular expressions
given helper script err.sh for runcmd when I run sh err.sh hello, world then stderr matches regex world$
5 Check output doesn’t have what we want to avoid
These scenarios verify that the stdout or stderr do not have something we want to avoid.
5.1 Check stdout is not exactly something
when I run echo hi then stdout isn't exactly "hello, world\n"
5.2 Check stderr is not exactly something
given helper script err.sh for runcmd when I run sh err.sh hi then stderr isn't exactly "hello, world\n"
5.3 Check stdout doesn’t contain sub-string
when I run echo hi then stdout doesn't contain "world"
5.4 Check stderr doesn’t contain sub-string
given helper script err.sh for runcmd when I run sh err.sh hi then stderr doesn't contain "world"
5.5 Check stdout doesn’t match regular expression
when I run echo hi then stdout doesn't match regex world$
5.6 Check stderr doesn’t match regular expressions
given helper script err.sh for runcmd when I run sh err.sh hi then stderr doesn't match regex world$