Problems adding neotest to the neovim template

[LauritzThaulow]

Heads up: I'm a nix noob and a neovim noob. I'm probably doing something stupid, but I've been struggling for a long time. I've tried to make a minimal example of what goes wrong, and one that is as foolproof as I can make it by not relying on any lazy loading magic. Here's what I've changed compared to what's in templates/neovim:

index 0c0e9c5..4180b90 100644
--- a/templates/neovim/flake.nix
+++ b/templates/neovim/flake.nix
@@ -72,2 +72,19 @@
       };
+      devShells = forAllSystems (
+        system:
+        let
+          myNeovim = self.packages.${system}.neovim;
+          pkgs = import nixpkgs { inherit system; };
+        in
+        {
+          default = pkgs.mkShell {
+            buildInputs = [
+              myNeovim
+              pkgs.python3Packages.pytest
+            ];
+            shellHook = ''
+              echo "Welcome to your Neovim dev environment!"
+            '';
+          };
+        });
     };
diff --git a/templates/neovim/init.lua b/templates/neovim/init.lua
index 1167998..e1baa37 100644
--- a/templates/neovim/init.lua
+++ b/templates/neovim/init.lua
@@ -220,2 +220,23 @@ vim.keymap.set("x", "<leader>P", '"_dP', { noremap = true, silent = true, desc =
 
+require("neotest").setup({
+  adapters = {
+    require("neotest-python")({
+      dap = { justMyCode = false },
+    }),
+  },
+})
+local nt = require("neotest")
+vim.keymap.set("n", "<leader>Tr", function() nt.run.run() end,
+  { desc = "[T]est [R]un nearest" })
+vim.keymap.set("n", "<leader>TT", function() nt.run.run(vim.fn.expand("%")) end,
+  { desc = "[T]est run [T]his file" })
+vim.keymap.set("n", "<leader>Ts", function() nt.summary.open() end,
+  { desc = "[T]est [S]ummary" })
+vim.keymap.set("n", "<leader>To", function() nt.output.open({ enter = true }) end,
+  { desc = "[T]est [O]utput" })
+vim.keymap.set("n", "<leader>Tp", function() nt.output_panel.open() end,
+  { desc = "[T]est output [P]anel" })
+vim.keymap.set("n", "<leader>Tl", function() nt.run.run_last() end,
+  { desc = "[T]est run [L]ast" })
+
 -- NOTE: You will likely want to break this up into more files.
@@ -958,2 +979,4 @@ nixInfo.lze.load {
         { "<leader>w_", hidden = true },
+        { "<leader>T", group = "[T]est" },
+        { "<leader>T_", hidden = true },
       }
diff --git a/templates/neovim/module.nix b/templates/neovim/module.nix
index e861373..5ac9771 100644
--- a/templates/neovim/module.nix
+++ b/templates/neovim/module.nix
@@ -163,2 +163,7 @@ inputs:
       # ))
+      nvim-nio  # neotest dep
+      plenary-nvim  # neotest dep
+      FixCursorHold-nvim  # neotest dep
+      neotest
+      neotest-python
     ];
diff --git a/templates/neovim/test_x.py b/templates/neovim/test_x.py
new file mode 100644
index 0000000..9842ae4
--- /dev/null
+++ b/templates/neovim/test_x.py
@@ -0,0 +1,4 @@
+
+def test_x():
+    assert False
+

Running nix develop succeeds without problems. Then I run nvim, and I get this error:

Error detected while processing VIMINIT:
E5108: Error executing lua /nix/store/9b3z5iq6388gnxfj4x2gmgd2yw2zga5r-neovim/init.lua:221: module 'neotest' not found:
        no field package.preload['neotest']
        cache_loader: module 'neotest' not found
        cache_loader_lib: module 'neotest' not found
        no file '/nix/store/xrv4dzvzdbxxdgyhn037i1pd6x4qfhx6-luajit-2.1.1741730670-env/share/lua/5.1/neotest.lua'
        no file '/nix/store/xrv4dzvzdbxxdgyhn037i1pd6x4qfhx6-luajit-2.1.1741730670-env/share/lua/5.1/neotest/init.lua'
        no file './neotest.lua'
        no file '/nix/store/7rk2ic67w77kvirns0c14151q253jxra-luajit-2.1.1741730670/share/luajit-2.1/neotest.lua'
        no file '/usr/local/share/lua/5.1/neotest.lua'
        no file '/usr/local/share/lua/5.1/neotest/init.lua'
        no file '/nix/store/7rk2ic67w77kvirns0c14151q253jxra-luajit-2.1.1741730670/share/lua/5.1/neotest.lua'
        no file '/nix/store/7rk2ic67w77kvirns0c14151q253jxra-luajit-2.1.1741730670/share/lua/5.1/neotest/init.lua'
        no file './neotest.lua'
        no file '/nix/store/7rk2ic67w77kvirns0c14151q253jxra-luajit-2.1.1741730670/share/luajit-2.1/neotest.lua'
        no file '/usr/local/share/lua/5.1/neotest.lua'
        no file '/usr/local/share/lua/5.1/neotest/init.lua'
        no file '/nix/store/7rk2ic67w77kvirns0c14151q253jxra-luajit-2.1.1741730670/share/lua/5.1/neotest.lua'
        no file '/nix/store/7rk2ic67w77kvirns0c14151q253jxra-luajit-2.1.1741730670/share/lua/5.1/neotest/init.lua'
        no file '/nix/store/7rk2ic67w77kvirns0c14151q253jxra-luajit-2.1.1741730670/share/lua/5.1/neotest.lua'
        no file '/nix/store/9rv605zd6csp2874s052s5gwnlg3z85a-luajit2.1-luassert-1.9.0-1/share/lua/5.1/neotest.lua'
        no file '/nix/store/9rv605zd6csp2874s052s5gwnlg3z85a-luajit2.1-luassert-1.9.0-1/share/lua/5.1/neotest/init.lua'
        no file '/nix/store/36zhbsfbn626zx2cmmin3knwil1m1icy-luajit2.1-say-1.4.1-3/share/lua/5.1/neotest.lua'
        no file '/nix/store/36zhbsfbn626zx2cmmin3knwil1m1icy-luajit2.1-say-1.4.1-3/share/lua/5.1/neotest/init.lua'
        no file '/nix/store/f2yw282a4wrcz0bkr50nw32kb5wdpah7-luajit2.1-nvim-nio-1.10.1-1/share/lua/5.1/neotest.lua'
        no file '/nix/store/f2yw282a4wrcz0bkr50nw32kb5wdpah7-luajit2.1-nvim-nio-1.10.1-1/share/lua/5.1/neotest/init.lua'
        no file '/nix/store/w31li55i13wnzv45m7gl9cm7c6fl6kdw-luajit2.1-plenary.nvim-scm-1/share/lua/5.1/neotest.lua'
        no file '/nix/store/w31li55i13wnzv45m7gl9cm7c6fl6kdw-luajit2.1-plenary.nvim-scm-1/share/lua/5.1/neotest/init.lua'
        no file '/nix/store/xrv4dzvzdbxxdgyhn037i1pd6x4qfhx6-luajit-2.1.1741730670-env/lib/lua/5.1/neotest.so'
        no file './neotest.so'

To find out where it should have looked, I looked at the output of the :lua nixInfo.lze.debug.display(nixInfo.plugins) command:

{  
  lazy = {    
    ["FixCursorHold.nvim"] = "/nix/store/7hrjs24xyyyy82k7d17szims1i35ndby-vimplugin-FixCursorHold.nvim-0-unstable-2023-02-13",    
    ["blink.cmp"] = "/nix/store/mq8vwpwq37x2ix1fymljsa36h8hv29f3-vimplugin-blink.cmp-1.9.1",    
    ["blink.compat"] = "/nix/store/x8wmy7d82xx3kfjgi83wfg0r39jn0bkb-vimplugin-blink.compat-2.5.0-unstable-2025-05-28",  
    <SNIP>
    ["lualine.nvim"] = "/nix/store/sv66hnwnp07nayrffrajb9f55fi7023p-vimplugin-luajit2.1-lualine.nvim-scm-1-unstable-scm-1",    
    neotest = "/nix/store/ahgsg7y0ic58vaskc7z4b1wy905xgadr-vimplugin-luajit2.1-neotest-5.13.4-1-unstable-5.13.4-1",    
    ["neotest-python"] = "/nix/store/k66s9sxavpp1a3lcg2x52gv1s398x6m1-vimplugin-neotest-python-0-unstable-2025-10-13",    
    <SNIP>
    ["which-key.nvim"] = "/nix/store/4xri7npn3pb4na89ss39q9xy9xswpqc7-vimplugin-which-key.nvim-3.17.0-unstable-2025-10-28"  
  },  
  start = {    
    COLLATED_TS_GRAMMARS = "/nix/store/rldyrlvrj6ynhdaqfas5a0drn7zf2z3l-COLLATED_TS_GRAMMARS",    
    lze = "/nix/store/7n3ip884fgk027a8md4iqx1glh7kpd91-vimplugin-lze-20260301035102",    
    lzextras = "/nix/store/n7wln43d4zdyhzgg3f1p9iq8h4d0c00d-vimplugin-lzextras-20260301034957",    
    ["vim-sleuth"] = "/nix/store/kiww7k4ikqvz17ns02202p5bfzcfrsmn-vimplugin-vim-sleuth-2.0-unstable-2024-09-19"  
  }
}

Notice that the neotest key is different from all the other plugins, in that it's not wrapped in square brackets and double quotes. Looking at that nix store path, the plugin files appear to be there, but for some reason nvim doesn't find them:

/nix/store/ahgsg7y0ic58vaskc7z4b1wy905xgadr-vimplugin-luajit2.1-neotest-5.13.4-1-unstable-5.13.4-1$ find -type f
./nix-support/propagated-build-inputs
./plugin/neotest.lua
./doc/tags
./doc/neotest.txt
./rock_manifest
./neotest-5.13.4-1.rockspec
./neotest-5.13.4-1-unstable-5.13.4-1-rocks/neotest/5.13.4-1/plugin/neotest.lua
./neotest-5.13.4-1-unstable-5.13.4-1-rocks/neotest/5.13.4-1/doc/neotest.txt
./neotest-5.13.4-1-unstable-5.13.4-1-rocks/neotest/5.13.4-1/rock_manifest
./neotest-5.13.4-1-unstable-5.13.4-1-rocks/neotest/5.13.4-1/neotest-5.13.4-1.rockspec
./neotest-5.13.4-1-unstable-5.13.4-1-rocks/manifest
./lua/neotest/consumers/state/tracker.lua
<SNIP>
./lua/neotest/init.lua
<SNIP>
./lua/neotest/client/strategies/dap/init.lua
./lua/neotest/logging.lua

I've had a long debugging session with Claude Opus, and I thought it might be relevant to know what it eventually concluded:

The nix-wrapper-modules neovim wrapper is silently dropping neotest because it's a luarocks-based plugin rather than a plain vim plugin. It's being included in the Nix evaluation (it shows up in the nixInfo.lze.debug.display output), but never actually makes it onto the runtime path.

Is Claude right? It suggested several workarounds but none of them solved the issue. How can I make the neotest plugin work?

Thank you for reading and considering this issue.

[BirdeeHub]

You have it installed lazily via nix, so it is in a pack/*/opt/neotest directory on the packpath instead of a pack/*/start/neotest directory, but you are not calling vim.cmd.packadd on it before trying to require it.

Thus, it is not yet on the runtimepath when you try to require it.

Either install it as a startup plugin, or packadd it first (or put it in an lze spec which will packadd it for you on some trigger of your choosing)

In the spec you added it to, the items in the list default to lazy = true because it was set up like

  config.specs.general = {
    lazy = true;
    data = with pkgs.vimPlugins; [ some list of plugins ];
  };

You can override it per item

  config.specs.general = {
    lazy = true;
    data = with pkgs.vimPlugins; [ some list of plugins { lazy = false; data = plugin-for-start-instead; } ];
  };

Or make a list which does not default to lazy = true

  config.specs.startupplugins = {
    # lazy = false; # <- the default, unless you have been messing with the global default via specMods
    data = with pkgs.vimPlugins; [ some list of plugins ];
  };

or equivalently, because lazy = false is the default for all of them unless you set it for that list in particular

  config.specs.startupplugins = with pkgs.vimPlugins; [ some list of plugins ];

---

Notice that the neotest key is different from all the other plugins, in that it's not wrapped in square brackets and double quotes.

That is just vim.inspect. All the characters in neotest are valid lua identifier characters so it does not need the brackets or quotes when it prints it out. You will see the same behavior with :=nixInfo.plugins it will just look worse because it would just print straight to the terminal instead of a floating buffer with highlighting

However, notice that it is in the lazy section of that printout. But you have not called vim.cmd.packadd('neotest') so it is not yet loaded. So require fails.

---

And no, claude is definitely not correct. The item you are installing is from the pkgs.vimPlugins set, it has already been converted to a neovim plugin. It is to be installed like any other neovim plugin.

It is correct about it not being on the runtimepath, but that is because you have it on the packpath in a lazily loaded location and need to call vim.cmd.packadd on it for it to be on the runtimepath. Not because of any quirks about how it is packaged and being a luarocks package or not.

If the item you were installing were NOT in the pkgs.vimPlugins set, and was instead from, say, pkgs.luajitPackages then it would be correct and you would config.settings.nvim_lua_env = lp: [ lp.thepackageinquestion ]; to install it like a lua package rather than a neovim plugin. But that is not the case here

and if it were a full program you wanted to add to PATH you would config.extraPackages = [ pkgs.thepackageinquestion ];

But that is also not the case here (although using config.extraPackages might remove your need for a dev shell for pytest in your example reproduction. It will suffix it to the path, so if a dev shell adds it too, the dev shell will win, but if it doesn't then it would use the one your wrapper provided)