Improved tests for svn_available?

Library/Homebrew/test/utils/svn_spec.rb

@@ -2,11 +2,17 @@ require "utils/svn"
 
 describe Utils do
   describe "#self.svn_available?" do
-    it "processes value when @svn is not defined" do
+    it "returns true if svn --version command succeeds" do
+      allow_any_instance_of(Process::Status).to receive(:success?).and_return(true)
       expect(described_class.svn_available?).to be_truthy
     end
 
-    it "returns value of @svn when @svn is defined" do
+    it "returns false if svn --version command does not succeed" do
+      allow_any_instance_of(Process::Status).to receive(:success?).and_return(false)
+      expect(described_class.svn_available?).to be_falsey
+    end
+
+    it "returns svn version if already set" do
       described_class.instance_variable_set(:@svn, true)
       expect(described_class.svn_available?).to be_truthy
     end
@@ -15,17 +21,16 @@ describe Utils do
   describe "#self.svn_remote_exists" do
     let(:url) { "https://dl.bintray.com/homebrew/mirror/" }
 
-    it "gives true when @svn is false" do
-      allow_any_instance_of(Process::Status).to receive(:success?).and_return(false)
+    it "returns true when svn is not available" do
       described_class.instance_variable_set(:@svn, false)
       expect(described_class.svn_remote_exists(url)).to be_truthy
     end
 
-    it "gives false when url is obscure" do
-      expect(described_class.svn_remote_exists(url)).to be_falsy
+    it "returns false when remote does not exist" do
+      expect(described_class.svn_remote_exists(url)).to be_falsey
     end
 
-    it "gives true when quiet_system succeeds with given url" do
+    it "returns true when remote exists" do
       allow_any_instance_of(Process::Status).to receive(:success?).and_return(true)
       expect(described_class.svn_remote_exists(url)).to be_truthy
     end

Library/Homebrew/utils/svn.rb

@@ -1,7 +1,6 @@
 module Utils
   def self.svn_available?
-    return @svn if instance_variable_defined?(:@svn)
-    @svn = quiet_system HOMEBREW_SHIMS_PATH/"scm/svn", "--version"
+    @svn ||= quiet_system HOMEBREW_SHIMS_PATH/"scm/svn", "--version"
   end
 
   def self.svn_remote_exists(url)