diff --git a/lib/default.nix b/lib/default.nix
index a5809c9..d9c64df 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -187,6 +187,10 @@ rec {
       # Themes
       vimPlugins.catppuccin-nvim
 
+      vimPlugins.conf-vim
+      vimPlugins.edit-alternate-vim
+      vimPlugins.standard-vim
+
       # Configuration.
       opdavies-nvim
     ];
diff --git a/overlays/vim-plugins.nix b/overlays/vim-plugins.nix
index ff9c6f7..8130ba2 100644
--- a/overlays/vim-plugins.nix
+++ b/overlays/vim-plugins.nix
@@ -1,5 +1,35 @@
 final: prev: {
   vimPlugins = prev.vimPlugins // {
+    conf-vim = final.vimUtils.buildVimPlugin {
+      name = "conf-vim";
+      src = final.fetchFromGitHub {
+        owner = "tjdevries";
+        repo = "conf.vim";
+        rev = "master";
+        sha256 = "AjiTJsoim0BAnyfqk1IQzNsa6jhFM2+A66E7q9sJqz0=";
+      };
+    };
+
+    edit-alternate-vim = final.vimUtils.buildVimPlugin {
+      name = "edit-alternate-vim";
+      src = final.fetchFromGitHub {
+        owner = "tjdevries";
+        repo = "edit_alternate.vim";
+        rev = "master";
+        sha256 = "mEKnqYAhgrdxPRoKf4S4yYecdFIHGg8bDxpqPuC1+S4=";
+      };
+    };
+
+    standard-vim = final.vimUtils.buildVimPlugin {
+      name = "standard-vim";
+      src = final.fetchFromGitHub {
+        owner = "tjdevries";
+        repo = "standard.vim";
+        rev = "master";
+        sha256 = "9VwkvV1Dv6cE4uDkPp36DozjWJOclDR883yDMYw000E=";
+      };
+    };
+
     tabline-vim = final.vimUtils.buildVimPlugin {
       name = "tabline-vim";
       src = final.fetchFromGitHub {
diff --git a/plugin/edit_alternate.lua b/plugin/edit_alternate.lua
new file mode 100644
index 0000000..293a28b
--- /dev/null
+++ b/plugin/edit_alternate.lua
@@ -0,0 +1,40 @@
+vim.fn["edit_alternate#rule#add"]("php", function(filename)
+  if filename:find "Test.php$" then
+    filename = filename:gsub("Test.php$", ".php")
+
+    if filename:find "tests/src/" then
+      -- Drupal tests. Remove the `src/{type}` from the path.
+      return filename:gsub("tests/src/(.-)/", "src/")
+    else
+      return filename:gsub("tests/", "src/")
+    end
+  else
+    filename = filename:gsub(".php$", "Test.php")
+
+    if filename:find "modules/custom" then
+      -- Drupal test types.
+      local test_types = { "Functional", "FunctionalJavaScript", "Kernel", "Unit" }
+
+      for _, test_type in ipairs(test_types) do
+        local filename_with_test_type = filename:gsub("src/", string.format("tests/src/%s/", test_type))
+
+        -- Return the first matching test file that exists.
+        if vim.fn.filereadable(filename_with_test_type) == 1 then
+          return filename_with_test_type
+        end
+      end
+    end
+  end
+end)
+
+if vim.fn.filereadable "fractal.config.js" == 1 then
+  vim.fn["edit_alternate#rule#add"]("twig", function(filename)
+    return (filename:gsub("%.twig$", ".config.yml"))
+  end)
+
+  vim.fn["edit_alternate#rule#add"]("yml", function(filename)
+    return (filename:gsub("%.config.yml$", ".twig"))
+  end)
+end
+
+vim.keymap.set("n", "<leader>ea", "<CMD>EditAlternate<CR>", { silent = true })