plugin/cache: Add cache disable option (#5540)

* add cache disable options

Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

plugin/cache/setup_test.go

@@ -192,3 +192,42 @@ func TestServfail(t *testing.T) {
 		}
 	}
 }
+
+func TestDisable(t *testing.T) {
+	tests := []struct {
+		input     string
+		shouldErr bool
+		nexcept   []string
+		pexcept   []string
+	}{
+		// positive
+		{"disable denial example.com example.org", false, []string{"example.com.", "example.org."}, nil},
+		{"disable success example.com example.org", false, nil, []string{"example.com.", "example.org."}},
+		{"disable denial", false, []string{"."}, nil},
+		{"disable success", false, nil, []string{"."}},
+		{"disable denial example.com example.org\ndisable success example.com example.org", false,
+			[]string{"example.com.", "example.org."}, []string{"example.com.", "example.org."}},
+		// negative
+		{"disable invalid example.com example.org", true, nil, nil},
+	}
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", fmt.Sprintf("cache {\n%s\n}", test.input))
+		ca, err := cacheParse(c)
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %v: Expected error but found nil", i)
+			continue
+		} else if !test.shouldErr && err != nil {
+			t.Errorf("Test %v: Expected no error but found error: %v", i, err)
+			continue
+		}
+		if test.shouldErr {
+			continue
+		}
+		if fmt.Sprintf("%v", test.nexcept) != fmt.Sprintf("%v", ca.nexcept) {
+			t.Errorf("Test %v: Expected %v but got: %v", i, test.nexcept, ca.nexcept)
+		}
+		if fmt.Sprintf("%v", test.pexcept) != fmt.Sprintf("%v", ca.pexcept) {
+			t.Errorf("Test %v: Expected %v but got: %v", i, test.pexcept, ca.pexcept)
+		}
+	}
+}