diff --git a/pkg/operations/set_test.go b/pkg/operations/set_test.go
new file mode 100644
index 0000000..e9c6e50
--- /dev/null
+++ b/pkg/operations/set_test.go
@@ -0,0 +1,81 @@
+package operations
+
+import (
+	"testing"
+
+	"github.com/alecthomas/assert/v2"
+	"github.com/can3p/sackmesser/pkg/traverse/simplejson"
+)
+
+func TestSetOperation(t *testing.T) {
+	jstr := `{ "abc": { "def": [ 1, 2, 3 ] } }`
+
+	examples := []struct {
+		description string
+		path        []string
+		arg         any
+		expected    string
+		isErr       bool
+	}{
+		{
+			description: "set existing field bool",
+			path:        []string{"abc"},
+			arg:         true,
+			expected:    `{ "abc": true }`,
+		},
+		// not testing integers since json parser parses everything into floats
+		// by default
+		{
+			description: "set existing field number",
+			path:        []string{"abc"},
+			arg:         1234.0,
+			expected:    `{ "abc": 1234.0 }`,
+		},
+		{
+			description: "set existing field string",
+			path:        []string{"abc"},
+			arg:         "test",
+			expected:    `{ "abc": "test" }`,
+		},
+		{
+			description: "set existing field null",
+			path:        []string{"abc"},
+			arg:         nil,
+			expected:    `{ "abc": null }`,
+		},
+		{
+			description: "set existing field json",
+			path:        []string{"abc"},
+			arg:         map[string]any{"one": "two"},
+			expected:    `{ "abc": { "one": "two" } }`,
+		},
+		{
+			description: "set new field",
+			path:        []string{"new field"},
+			arg:         true,
+			expected:    `{ "abc": { "def": [ 1, 2, 3 ] }, "new field": true }`,
+		},
+		{
+			description: "set array field",
+			path:        []string{"abc", "def", "0"},
+			arg:         true,
+			expected:    `{ "abc": { "def": [ true, 2, 3 ] } }`,
+		},
+	}
+
+	for idx, ex := range examples {
+		node := simplejson.MustParse([]byte(jstr))
+
+		err := Set(node, ex.path, ex.arg)
+
+		if ex.isErr {
+			assert.Error(t, err, "[Ex %d - %s]", idx+1, ex.description)
+			continue
+		}
+
+		expected := simplejson.MustParse([]byte(ex.expected))
+
+		assert.Equal(t, expected.Value(), node.Value(), "[Ex %d - %s]", idx+1, ex.description)
+	}
+
+}