Add agent library

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/agent/result_test.go

@@ -0,0 +1,91 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package agent_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.probo.inc/probo/pkg/agent"
+	"go.probo.inc/probo/pkg/llm"
+)
+
+func TestResult_FinalMessage(t *testing.T) {
+	t.Parallel()
+
+	t.Run(
+		"returns zero value when messages is empty",
+		func(t *testing.T) {
+			t.Parallel()
+
+			r := &agent.Result{}
+			msg := r.FinalMessage()
+
+			assert.Equal(t, llm.Message{}, msg)
+			assert.Equal(t, "", msg.Text())
+		},
+	)
+
+	t.Run(
+		"returns the last message with single message",
+		func(t *testing.T) {
+			t.Parallel()
+
+			r := &agent.Result{
+				Messages: []llm.Message{
+					assistantMessage("Hello!"),
+				},
+			}
+
+			assert.Equal(t, "Hello!", r.FinalMessage().Text())
+		},
+	)
+
+	t.Run(
+		"returns the last message with multiple messages",
+		func(t *testing.T) {
+			t.Parallel()
+
+			r := &agent.Result{
+				Messages: []llm.Message{
+					userMessage("Hi"),
+					assistantMessage("Hello!"),
+					userMessage("How are you?"),
+					assistantMessage("I'm fine."),
+				},
+			}
+
+			assert.Equal(t, "I'm fine.", r.FinalMessage().Text())
+		},
+	)
+
+	t.Run(
+		"returns message regardless of role",
+		func(t *testing.T) {
+			t.Parallel()
+
+			r := &agent.Result{
+				Messages: []llm.Message{
+					assistantMessage("first"),
+					userMessage("last user message"),
+				},
+			}
+
+			msg := r.FinalMessage()
+			assert.Equal(t, llm.RoleUser, msg.Role)
+			assert.Equal(t, "last user message", msg.Text())
+		},
+	)
+}