Convert brew --cellar test to spec.

Library/Homebrew/test/cellar_formula_test.rb

@@ -1,8 +0,0 @@
-require "testing_env"
-
-class IntegrationCommandTestCellarFormula < IntegrationCommandTestCase
-  def test_cellar_formula
-    assert_match "#{HOMEBREW_CELLAR}/testball",
-                 cmd("--cellar", testball)
-  end
-end

Library/Homebrew/test/cellar_test.rb

@@ -1,8 +0,0 @@
-require "testing_env"
-
-class IntegrationCommandTestCellar < IntegrationCommandTestCase
-  def test_cellar
-    assert_equal HOMEBREW_CELLAR.to_s,
-                 cmd("--cellar")
-  end
-end

Library/Homebrew/test/cmd/--cellar_spec.rb

@@ -0,0 +1,15 @@
+describe "brew --cellar", :integration_test do
+  it "print the location of Homebrew's Cellar when no argument is given" do
+    expect { brew "--cellar" }
+      .to output("#{HOMEBREW_CELLAR}\n").to_stdout
+      .and not_to_output.to_stderr
+      .and be_a_success
+  end
+
+  it "returns the Cellar subdirectory for a given Formula" do
+    expect { brew "--cellar", testball }
+      .to output(%r{#{HOMEBREW_CELLAR}/testball}).to_stdout
+      .and not_to_output.to_stderr
+      .and be_a_success
+  end
+end