more tests

lib/ecto.ex

@@ -231,6 +231,10 @@ defmodule Testcontainers.Ecto do
           repo
       end
 
+    if not :erlang.function_exported(repo, :__info__, 1) do
+      raise ArgumentError, "Repo is invalid: repo=#{inspect(repo)}"
+    end
+
     user = Keyword.get(options, :user, "test")
     password = Keyword.get(options, :password, "test")
     database = Keyword.get(options, :database, "#{Atom.to_string(app)}_test")

test/ecto_errors_test.exs

@@ -0,0 +1,31 @@
+defmodule Testcontainers.EctoMysqlTest do
+  use ExUnit.Case, async: true
+
+  import Testcontainers.Ecto
+
+  test "repo cannot be nil" do
+    assert_raise ArgumentError, "Repo is invalid: repo=Testcontainers.Repo", fn ->
+      mysql_container(
+        app: :testcontainers,
+        repo: nil
+      )
+    end
+  end
+
+  test "repo must be atom" do
+    assert_raise ArgumentError, "Not an atom: repo=\"hello\"", fn ->
+      mysql_container(
+        app: :testcontainers,
+        repo: "hello"
+      )
+    end
+  end
+
+  test "app must be atom" do
+    assert_raise ArgumentError, "Missing or not an atom: app=\"hello\"", fn ->
+      mysql_container(
+        app: "hello"
+      )
+    end
+  end
+end