Nice message for broken Erlang installs

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## v1.7.0 - 2025-10-28
+
+- A custom error is now emitted if Eunit is missing from the Erlang runtime.
+
 ## v1.6.2 - 2025-08-23
 
 - Fixed a bug where the number of passes was reported as the total number of

gleam.toml

@@ -1,5 +1,5 @@
 name = "gleeunit"
-version = "1.6.2"
+version = "1.7.0"
 licences = ["Apache-2.0"]
 description = "A simple test runner for Gleam, using EUnit on Erlang"
 repository = { type = "github", user = "lpil", repo = "gleeunit" }

src/gleeunit/internal/reporting.gleam

@@ -86,6 +86,17 @@ pub fn test_failed(
   State(..state, failed: state.failed + 1)
 }
 
+pub fn eunit_missing() -> Result(never, Nil) {
+  let message = bold(red("Error")) <> ": EUnit libraries not found.
+
+Your Erlang installation seems to be incomplete. If you installed Erlang using
+a package manager ensure that you have installed the full Erlang
+distribution instead of a stripped-down version.
+"
+  io.print_error(message)
+  Error(Nil)
+}
+
 fn format_unknown(
   module: String,
   function: String,

src/gleeunit_ffi.erl

@@ -7,8 +7,15 @@ find_files(Pattern, In) ->
   lists:map(fun list_to_binary/1, Results).
 
 run_eunit(Tests, Options) ->
-    case eunit:test({timeout, 60, Tests}, Options) of
-        ok -> {ok, nil};
-        error -> {error, nil};
-        {error, Term} -> {error, Term}
+    case code:which(eunit) of
+        non_existing ->
+            gleeunit@internal@reporting:eunit_missing();
+
+        _ -> 
+            case eunit:test({timeout, 60, Tests}, Options) of
+                ok -> {ok, nil};
+                error -> {error, nil};
+                {error, Term} -> {error, Term}
+            end
     end.
+

src/gleeunit_progress.erl

@@ -1,9 +1,7 @@
 %% A formatter adapted from Sean Cribb's https://github.com/seancribbs/eunit_formatters
 
 -module(gleeunit_progress).
--behaviour(eunit_listener).
 -define(NOTEST, true).
--include_lib("eunit/include/eunit.hrl").
 
 %% eunit_listener callbacks
 -export([