Added reverse op

pkg/yqlib/operator_reverse_test.go

@@ -0,0 +1,54 @@
+package yqlib
+
+import "testing"
+
+var reverseOperatorScenarios = []expressionScenario{
+	{
+		description: "Reverse",
+		document:    "[1, 2, 3]",
+		expression:  `reverse`,
+		expected: []string{
+			"D0, P[], (!!seq)::[3, 2, 1]\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   "[]",
+		expression: `reverse`,
+		expected: []string{
+			"D0, P[], (!!seq)::[]\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   "[1]",
+		expression: `reverse`,
+		expected: []string{
+			"D0, P[], (!!seq)::[1]\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   "[1,2]",
+		expression: `reverse`,
+		expected: []string{
+			"D0, P[], (!!seq)::[2, 1]\n",
+		},
+	},
+	{
+		description:    "Sort descending by string field",
+		subdescription: "Use sort with reverse to sort in descending order.",
+		document:       "[{a: banana},{a: cat},{a: apple}]",
+		expression:     `sort_by(.a) | reverse`,
+		expected: []string{
+			"D0, P[], (!!seq)::[{a: cat}, {a: banana}, {a: apple}]\n",
+		},
+	},
+}
+
+func TestReverseOperatorScenarios(t *testing.T) {
+	for _, tt := range reverseOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentOperatorScenarios(t, "reverse", reverseOperatorScenarios)
+}