Update the README testing example to one that works

README.md

@@ -482,9 +482,7 @@ context.
 ```ruby
 describe AuthenticateUser do
   describe "#call" do
-
-    let(:interactor) { AuthenticateUser.new(email: "john@example.com", password: "secret") }
-    let(:context) { interactor.context }
+    subject(:context) { AuthenticateUser.call(email: "john@example.com", password: "secret") }
 
     context "when given valid credentials" do
       let(:user) { double(:user, secret_token: "token") }
@@ -493,26 +491,14 @@ describe AuthenticateUser do
         allow(User).to receive(:authenticate).with("john@example.com", "secret").and_return(user)
       end
 
-      it "succeeds" do
-        interactor.call
-
-        expect(context).to be_a_success
-      end
+      it { is_expected.to be_a_success }
 
       it "provides the user" do
-        expect {
-          interactor.call
-        }.to change {
-          context.user
-        }.from(nil).to(user)
+        expect(subject.user).to eq(user)
       end
 
       it "provides the user's secret token" do
-        expect {
-          interactor.call
-        }.to change {
-          context.token
-        }.from(nil).to("token")
+        expect(subject.token).to eq("token")
       end
     end
 
@@ -521,18 +507,10 @@ describe AuthenticateUser do
         allow(User).to receive(:authenticate).with("john@example.com", "secret").and_return(nil)
       end
 
-      it "fails" do
-        interactor.call
-
-        expect(context).to be_a_failure
-      end
+      it { is_expected.to be_a_failure }
 
       it "provides a failure message" do
-        expect {
-          interactor.call
-        }.to change {
-          context.message
-        }.from(nil).to be_present
+        expect(subject.message).to be_present
       end
     end
   end

spec/readme_spec.rb

@@ -0,0 +1,52 @@
+class AuthenticateUser
+  include Interactor
+
+  def call
+    if user = User.authenticate(context.email, context.password)
+      context.user = user
+      context.token = user.secret_token
+    else
+      context.fail!(message: "authenticate_user.failure")
+    end
+  end
+end
+
+class User; end
+
+describe "The testing example from the README" do
+  describe AuthenticateUser do
+    describe "#call" do
+      subject(:context) { AuthenticateUser.call(email: "john@example.com", password: "secret") }
+
+      context "when given valid credentials" do
+        let(:user) { double(:user, secret_token: "token") }
+
+        before do
+          allow(User).to receive(:authenticate).with("john@example.com", "secret").and_return(user)
+        end
+
+        it { is_expected.to be_a_success }
+
+        it "provides the user" do
+          expect(subject.user).to eq(user)
+        end
+
+        it "provides the user's secret token" do
+          expect(subject.token).to eq("token")
+        end
+      end
+
+      context "when given invalid credentials" do
+        before do
+          allow(User).to receive(:authenticate).with("john@example.com", "secret").and_return(nil)
+        end
+
+        it { is_expected.to be_a_failure }
+
+        it "provides a failure message" do
+          expect(subject.message).to_not be_nil  # be_present requires activesupport
+        end
+      end
+    end
+  end
+end