Update cheatsheets

test

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# test
+
+> Check file types and compare values.
+> Returns 0 if the condition evaluates to true, 1 if it evaluates to false.
+> More information: <https://www.gnu.org/software/coreutils/test>.
+
+- Test if a given variable is equal to a given string:
+
+`test "{{$MY_VAR}}" = "{{/bin/zsh}}"`
+
+- Test if a given variable is empty:
+
+`test -z "{{$GIT_BRANCH}}"`
+
+- Test if a file exists:
+
+`test -f "{{path/to/file_or_directory}}"`
+
+- Test if a directory does not exist:
+
+`test ! -d "{{path/to/directory}}"`
+
+- If A is true, then do B, or C in the case of an error (notice that C may run even if A fails):
+
+`test {{condition}} && {{echo "true"}} || {{echo "false"}}`