diff --git a/Library/Homebrew/caveats.rb b/Library/Homebrew/caveats.rb
index 2d0ceeb481..578b292fab 100644
--- a/Library/Homebrew/caveats.rb
+++ b/Library/Homebrew/caveats.rb
@@ -164,20 +164,7 @@ class Caveats
   def plist_caveats
     s = []
     if f.plist || (keg && keg.plist_installed?)
-      destination = if f.plist_startup
-        "/Library/LaunchDaemons"
-      else
-        "~/Library/LaunchAgents"
-      end
-
-      plist_filename = if f.plist
-        f.plist_path.basename
-      else
-        File.basename Dir["#{keg}/*.plist"].first
-      end
       plist_domain = f.plist_path.basename(".plist")
-      destination_path = Pathname.new File.expand_path destination
-      plist_path = destination_path/plist_filename
 
       # we readlink because this path probably doesn't exist since caveats
       # occurs before the link step of installation
@@ -209,10 +196,29 @@ class Caveats
         s << "  #{f.plist_manual}"
       end
 
+      # pbpaste is the system clipboard tool on macOS and fails with `tmux` by default
+      # check if this is being run under `tmux` to avoid failing
       if ENV["TMUX"] && !quiet_system("/usr/bin/pbpaste")
         s << "" << "WARNING: brew services will fail when run under tmux."
       end
     end
     s.join("\n") + "\n" unless s.empty?
   end
+
+  def plist_path
+    destination = if f.plist_startup
+      "/Library/LaunchDaemons"
+    else
+      "~/Library/LaunchAgents"
+    end
+
+    plist_filename = if f.plist
+      f.plist_path.basename
+    else
+      File.basename Dir["#{keg}/*.plist"].first
+    end
+    destination_path = Pathname.new(File.expand_path(destination))
+
+    destination_path/plist_filename
+  end
 end
diff --git a/Library/Homebrew/test/caveats_spec.rb b/Library/Homebrew/test/caveats_spec.rb
index d8be9dc521..53c90d60a8 100644
--- a/Library/Homebrew/test/caveats_spec.rb
+++ b/Library/Homebrew/test/caveats_spec.rb
@@ -26,4 +26,220 @@ describe Caveats do
       expect(described_class.new(f)).not_to be_empty
     end
   end
+
+  describe "#caveats" do
+    context "when f.plist is not nil", :needs_macos do
+      it "prints plist startup information when f.plist_startup is not nil" do
+        f = formula do
+          url "foo-1.0"
+          def plist
+            "plist_test.plist"
+          end
+          plist_options startup: true
+        end
+        expect(described_class.new(f).caveats).to include("startup")
+      end
+
+      it "prints plist login information when f.plist_startup is nil" do
+        f = formula do
+          url "foo-1.0"
+          def plist
+            "plist_test.plist"
+          end
+        end
+        expect(described_class.new(f).caveats).to include("login")
+      end
+
+      it "gives information about restarting services after upgrade" do
+        f = formula do
+          url "foo-1.0"
+          def plist
+            "plist_test.plist"
+          end
+          plist_options startup: true
+        end
+        f_obj = described_class.new(f)
+        plist_path = Pathname.new("plist")
+        FileUtils.touch plist_path
+        allow(f_obj).to receive(:plist_path).and_return(plist_path)
+        allow(plist_path).to receive(:symlink?).and_return(true)
+        expect(f_obj.caveats).to include("restart #{f.full_name}")
+        expect(f_obj.caveats).to include("sudo")
+      end
+
+      context "when plist_path is not a file nor symlinked and plist_startup is false" do
+        let(:f) {
+          formula do
+            url "foo-1.0"
+            def plist
+              "plist_test.plist"
+            end
+          end
+        }
+        let(:f_obj) { described_class.new(f) }
+        let(:caveats) { f_obj.caveats }
+        let(:plist_path) { Pathname.new("plist") }
+
+        before do
+          FileUtils.touch plist_path
+          allow(f_obj).to receive(:plist_path).and_return(plist_path)
+          allow(plist_path).to receive(:symlink?).and_return(true)
+        end
+
+        it "tells command to run after upgrade" do
+          allow(Kernel).to receive(:system).with(any_args).and_return(true)
+          expect(caveats).to include("restart #{f.full_name} after an upgrade")
+        end
+
+        it "tells command to run to start formula" do
+          expect(caveats).to include("To start #{f.full_name}:")
+        end
+      end
+
+      it "gives information about plist_manual" do
+        f = formula do
+          url "foo-1.0"
+          def plist
+            "plist_test.plist"
+          end
+          plist_options manual: "foo"
+        end
+        caveats = described_class.new(f).caveats
+
+        expect(caveats).to include("background service")
+        expect(caveats).to include(f.plist_manual)
+      end
+
+      it "warns about brew failing under tmux" do
+        f = formula do
+          url "foo-1.0"
+          def plist
+            "plist_test.plist"
+          end
+        end
+        allow(ENV).to receive(:[]).with("TMUX").and_return(true)
+        allow(Homebrew).to receive(:_system).with("/usr/bin/pbpaste").and_return(false)
+        caveats = described_class.new(f).caveats
+
+        expect(caveats).to include("WARNING:")
+        expect(caveats).to include("tmux")
+      end
+    end
+
+    context "when f.keg_only is not nil" do
+      let(:f) {
+        formula do
+          url "foo-1.0"
+          keg_only "some reason"
+        end
+      }
+      let(:caveats) { described_class.new(f).caveats }
+
+      it "tells formula is keg_only" do
+        expect(caveats).to include("keg-only")
+      end
+
+      it "gives command to be run when f.bin is a directory" do
+        Pathname.new(f.bin).mkpath
+        expect(caveats).to include(f.opt_bin.to_s)
+      end
+
+      it "gives command to be run when f.sbin is a directory" do
+        Pathname.new(f.sbin).mkpath
+        expect(caveats).to include(f.opt_sbin.to_s)
+      end
+
+      context "when f.lib or f.include is a directory" do
+        it "gives command to be run when f.lib is a directory" do
+          Pathname.new(f.lib).mkpath
+          expect(caveats).to include("-L#{f.opt_lib}")
+        end
+
+        it "gives command to be run when f.include is a directory" do
+          Pathname.new(f.include).mkpath
+          expect(caveats).to include("-I#{f.opt_include}")
+        end
+
+        it "gives PKG_CONFIG_PATH when f.lib/'pkgconfig' and f.share/'pkgconfig' are directories" do
+          allow_any_instance_of(Object).to receive(:which).with(any_args).and_return(Pathname.new("blah"))
+
+          Pathname.new(f.share/"pkgconfig").mkpath
+          Pathname.new(f.lib/"pkgconfig").mkpath
+
+          expect(caveats).to include("#{f.opt_lib}/pkgconfig")
+          expect(caveats).to include("#{f.opt_share}/pkgconfig")
+        end
+      end
+    end
+
+    context "shell completions" do
+      let(:f) {
+        formula do
+          url "foo-1.0"
+        end
+      }
+      let(:caveats) { described_class.new(f).caveats }
+      let(:path) { f.prefix.resolved_path }
+
+      before do
+        allow_any_instance_of(Pathname).to receive(:children).and_return([Pathname.new("child")])
+        allow_any_instance_of(Object).to receive(:which).with(any_args).and_return(Pathname.new("shell"))
+      end
+
+      it "gives dir where bash completions have been installed" do
+        (path/"etc/bash_completion.d").mkpath
+        expect(caveats).to include(HOMEBREW_PREFIX/"etc/bash_completion.d")
+      end
+
+      it "gives dir where zsh completions have been installed" do
+        (path/"share/zsh/site-functions").mkpath
+        expect(caveats).to include(HOMEBREW_PREFIX/"share/zsh/site-functions")
+      end
+
+      it "gives dir where fish completions have been installed" do
+        (path/"share/fish/vendor_completions.d").mkpath
+        expect(caveats).to include(HOMEBREW_PREFIX/"share/fish/vendor_completions.d")
+      end
+    end
+
+    context "python caveats" do
+      before do
+        (f.prefix.resolved_path/"lib/python2.7/site-packages").mkpath
+      end
+
+      context "when f is not keg_only" do
+        let(:f) {
+          formula do
+            url "foo-1.0"
+          end
+        }
+        let(:caveats) { described_class.new(f).caveats }
+        let(:user_site_packages) { Language::Python.user_site_packages("python") }
+
+        it "give commands to run when Homebrew's site-packages is not in Python sys.path" do
+          expect(caveats).to include("Homebrew's site-packages is not\nin your Python sys.path")
+          expect(caveats).to include(user_site_packages)
+          expect(caveats).to include("import site")
+        end
+
+        it "gives commands to run when python pth files are installed" do
+          allow(Homebrew).to receive(:_system).and_return(true)
+          allow(Dir).to receive(:[]).with(any_args).and_return(["blah.pth"])
+          expect(caveats).to include(".pth files to Homebrew's site-packages and your\nPython isn't configured")
+          expect(caveats).to include(user_site_packages)
+          expect(caveats).to include("import site")
+        end
+      end
+
+      it "gives commands to run when formula is keg_only" do
+        f = formula do
+          url "foo-1.0"
+          keg_only "some reason"
+        end
+        caveats = described_class.new(f).caveats
+        homebrew_site_packages = Language::Python.homebrew_site_packages
+        expect(caveats).to include("echo #{f.opt_prefix}/lib/python2.7/site-packages >> #{homebrew_site_packages/f.name}.pth")
+      end
+    end
+  end
 end