move logic to find an executable from ConfigureOp to Util

spec/rscons/util_spec.rb

@@ -55,5 +55,61 @@ module Rscons
       end
     end
 
+    describe ".find_executable" do
+      context "when given a path with directory components" do
+        it "returns the path if it is executable" do
+          expect(File).to receive(:file?).with("a/path").and_return(true)
+          expect(File).to receive(:executable?).with("a/path").and_return(true)
+          expect(Util.find_executable("a/path")).to eq "a/path"
+        end
+
+        it "returns nil if the path is not executable" do
+          expect(File).to receive(:file?).with("a/path").and_return(true)
+          expect(File).to receive(:executable?).with("a/path").and_return(false)
+          expect(Util.find_executable("a/path")).to be_nil
+        end
+      end
+
+      context "when given a program name without directory components" do
+        context "on Windows" do
+          before(:each) do
+            stub_const("File::PATH_SEPARATOR", ";")
+            stub_const("RbConfig::CONFIG", "host_os" => "mingw")
+            expect(ENV).to receive(:[]).with("PATH").and_return("C:\\bin;C:\\Windows")
+            allow(Dir).to receive(:entries).with("C:\\bin").and_return(%w[one.com])
+            allow(Dir).to receive(:entries).with("C:\\Windows").and_return(%w[two.exe Three.bat])
+          end
+
+          it "returns a path to a .exe found" do
+            expect(File).to receive(:file?).with("C:\\Windows/two.exe").and_return(true)
+            expect(File).to receive(:executable?).with("C:\\Windows/two.exe").and_return(true)
+            expect(Util.find_executable("two")).to eq "C:\\Windows/two.exe"
+          end
+
+          it "returns a path to a .exe found including extension" do
+            expect(File).to receive(:file?).with("C:\\Windows/two.exe").and_return(true)
+            expect(File).to receive(:executable?).with("C:\\Windows/two.exe").and_return(true)
+            expect(Util.find_executable("TWO.EXE")).to eq "C:\\Windows/two.exe"
+          end
+
+          it "returns a path to a .com found" do
+            expect(File).to receive(:file?).with("C:\\bin/one.com").and_return(true)
+            expect(File).to receive(:executable?).with("C:\\bin/one.com").and_return(true)
+            expect(Util.find_executable("ONE")).to eq "C:\\bin/one.com"
+          end
+
+          it "returns a path to a .bat found" do
+            expect(File).to receive(:file?).with("C:\\Windows/Three.bat").and_return(true)
+            expect(File).to receive(:executable?).with("C:\\Windows/Three.bat").and_return(true)
+            expect(Util.find_executable("three")).to eq "C:\\Windows/Three.bat"
+          end
+
+          it "returns nil when nothing is found" do
+            expect(Util.find_executable("notthere")).to be_nil
+          end
+        end
+      end
+    end
+
   end
 end