Add spec for no .env files present

spec/fixtures/no_root_dotenv/.env.development.test

@@ -0,0 +1,5 @@
+DOTENV=.env.development.test
+ENV_VAR=.env.development.test
+DEVELOPMENT_TEST=.env.development.test
+DEVELOPMENT=.env.development.test
+TEST=.env.development.test

spec/load_dotenv_spec.rb

@@ -1,4 +1,6 @@
 RSpec.describe Foobara::LoadDotenv do
+  let(:dir) { "#{__dir__}/fixtures/test_dotenvs" }
+
   it "has a version number" do
     expect(Foobara::LoadDotenv::VERSION).to_not be_nil
   end
@@ -12,7 +14,7 @@
       let(:env) { "development" }
 
       it "applies .env.development.local" do
-        described_class.run!(env:, dir: "#{__dir__}/fixtures/test_dotenvs")
+        described_class.run!(env:, dir:)
 
         expect(Dotenv).to have_received(:load!).with(
           ".env.development.test.local",
@@ -23,6 +25,26 @@
           ".env"
         )
       end
+
+      context "when no .env files" do
+        let(:dir) { "#{__dir__}/fixtures/no_dotenvs" }
+
+        it "does nothing" do
+          expect {
+            described_class.run!(env:, dir:)
+          }.to_not raise_error
+        end
+      end
+
+      context "when no root .env file but there are others" do
+        let(:dir) { "#{__dir__}/fixtures/no_root_dotenv" }
+
+        it "does not try to load .env" do
+          described_class.run!(env:, dir:)
+
+          expect(Dotenv).to have_received(:load!).with(".env.development.test")
+        end
+      end
     end
   end
 end