chore: use mini.test plugin, and convert all tests

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
         run: |
           nvim --version
           [ ! -d tests ] && exit 0
-          ./tests/run
+          make test
   docs:
     if: github.ref == 'refs/heads/main'
     permissions:

.gitignore

@@ -1 +1,2 @@
 .tests
+deps/

CONTRIBUTING.md

@@ -67,4 +67,4 @@ The first and last line is the boundary for the curl command.
 
 Tests can be run like this:
 
-`./test/run`
+`make test`

Makefile

@@ -0,0 +1,16 @@
+# Run all test files
+test: deps/mini.nvim deps/plenary.nvim
+	nvim --headless --noplugin -u ./scripts/minimal_init.lua -c "lua MiniTest.run()"
+
+# Run test from file at `$FILE` environment variable
+test_file: deps/mini.nvim deps/plenary.nvim
+	nvim --headless --noplugin -u ./scripts/minimal_init.lua -c "lua MiniTest.run_file('$(FILE)')"
+
+# Download 'mini.nvim' to use its 'mini.test' testing module
+deps/mini.nvim:
+	@mkdir -p deps
+	git clone --filter=blob:none https://github.com/echasnovski/mini.nvim $@
+
+deps/plenary.nvim:
+	@mkdir -p deps
+	git clone --filter=blob:none https://github.com/nvim-lua/plenary.nvim $@

scripts/minimal_init.lua

@@ -0,0 +1,13 @@
+-- Add current directory to 'runtimepath' to be able to use 'lua' files
+vim.cmd([[let &rtp.=','.getcwd()]])
+
+-- Set up 'mini.test' only when calling headless Neovim (like with `make test`)
+if #vim.api.nvim_list_uis() == 0 then
+  -- Add 'mini.nvim' to 'runtimepath' to be able to use 'mini.test'
+  -- Assumed that 'mini.nvim' is stored in 'deps/mini.nvim'
+  vim.cmd("set rtp+=deps/mini.nvim")
+  vim.cmd("set rtp+=deps/plenary.nvim")
+
+  -- Set up 'mini.test'
+  require("mini.test").setup()
+end

stylua.toml

@@ -0,0 +1,3 @@
+indent_type = "Spaces"
+indent_width = 2
+column_width = 120