fix: always respect file importance order

lib/dotenv.rb

@@ -29,7 +29,7 @@ def load!(*filenames)
 
   # same as `load`, but will override existing values in `ENV`
   def overload(*filenames)
-    with(*filenames) do |f|
+    with(*filenames.reverse) do |f|
       ignoring_nonexistent_files do
         env = Environment.new(f, false)
         instrument("dotenv.overload", env: env) { env.apply! }
@@ -39,7 +39,7 @@ def overload(*filenames)
 
   # same as `overload`, but raises Errno::ENOENT if any files don't exist
   def overload!(*filenames)
-    with(*filenames) do |f|
+    with(*filenames.reverse) do |f|
       env = Environment.new(f, false)
       instrument("dotenv.overload", env: env) { env.apply! }
     end

spec/dotenv/rails_spec.rb

@@ -113,8 +113,8 @@ def add(*items)
       )
     end
 
-    it "overloads .env.test with .env" do
-      expect(ENV["DOTENV"]).to eql("true")
+    it "overloads .env with .env.test" do
+      expect(ENV["DOTENV"]).to eql("test")
     end
 
     context "when loading a file containing already set variables" do
@@ -125,7 +125,7 @@ def add(*items)
 
         expect do
           subject
-        end.to(change { ENV["DOTENV"] }.from("predefined").to("true"))
+        end.to(change { ENV["DOTENV"] }.from("predefined").to("test"))
       end
     end
   end

spec/dotenv_spec.rb

@@ -54,6 +54,30 @@
     end
   end
 
+  shared_examples "overload" do
+    context "with multiple files" do
+      let(:env_files) { [fixture_path("important.env"), fixture_path("plain.env")] }
+
+      let(:expected) do
+        {
+          "OPTION_A" => "abc",
+          "OPTION_B" => "2",
+          "OPTION_C" => "3",
+          "OPTION_D" => "4",
+          "OPTION_E" => "5",
+          "PLAIN" => "false"
+        }
+      end
+
+      it "respects the file importance order" do
+        subject
+        expected.each do |key, value|
+          expect(ENV[key]).to eq(value)
+        end
+      end
+    end
+  end
+
   describe "load" do
     let(:env_files) { [] }
     subject { Dotenv.load(*env_files) }
@@ -101,6 +125,7 @@
     let(:env_files) { [fixture_path("plain.env")] }
     subject { Dotenv.overload(*env_files) }
     it_behaves_like "load"
+    it_behaves_like "overload"
 
     it "initializes the Environment with a falsey is_load" do
       expect(Dotenv::Environment).to receive(:new).with(anything, false)
@@ -134,6 +159,7 @@
     let(:env_files) { [fixture_path("plain.env")] }
     subject { Dotenv.overload!(*env_files) }
     it_behaves_like "load"
+    it_behaves_like "overload"
 
     it "initializes the Environment with a falsey is_load" do
       expect(Dotenv::Environment).to receive(:new).with(anything, false)

spec/fixtures/important.env

@@ -0,0 +1,3 @@
+PLAIN=false
+OPTION_A=abc
+OPTION_B=2