test: cover DeepSeek Vision image payload

tests/unit/deepseek-vision.test.ts

@@ -0,0 +1,90 @@
+import { createDeepSeek } from "@ai-sdk/deepseek"
+import { generateText } from "ai"
+import { describe, expect, it } from "vitest"
+
+describe("DeepSeek V4 Vision image input", () => {
+    it("includes image content in the chat completion request", async () => {
+        let requestBody:
+            | {
+                  messages: Array<{
+                      role: string
+                      content: string | Array<Record<string, unknown>>
+                  }>
+              }
+            | undefined
+
+        const provider = createDeepSeek({
+            apiKey: "test-key",
+            baseURL: "https://example.test",
+            fetch: async (_input, init) => {
+                const body = init?.body
+                const rawBody =
+                    typeof body === "string"
+                        ? body
+                        : new TextDecoder().decode(body as Uint8Array)
+                requestBody = JSON.parse(rawBody)
+
+                return new Response(
+                    JSON.stringify({
+                        id: "test-response",
+                        object: "chat.completion",
+                        created: 1,
+                        model: "deepseek-v4-flash-vision-exp",
+                        choices: [
+                            {
+                                index: 0,
+                                message: { role: "assistant", content: "ok" },
+                                finish_reason: "stop",
+                            },
+                        ],
+                        usage: {
+                            prompt_tokens: 1,
+                            completion_tokens: 1,
+                            total_tokens: 2,
+                        },
+                    }),
+                    {
+                        status: 200,
+                        headers: { "content-type": "application/json" },
+                    },
+                )
+            },
+        })
+
+        await generateText({
+            model: provider("deepseek-v4-flash-vision-exp"),
+            messages: [
+                {
+                    role: "user",
+                    content: [
+                        { type: "text", text: "Describe this image." },
+                        {
+                            type: "image",
+                            image: "data:image/png;base64,aGVsbG8=",
+                            mediaType: "image/png",
+                        },
+                    ],
+                },
+            ],
+        })
+
+        if (requestBody === undefined) {
+            throw new Error("DeepSeek request was not captured")
+        }
+
+        const userMessage = requestBody.messages.find(
+            (message) => message.role === "user",
+        )
+        expect(userMessage?.content).toEqual(
+            expect.arrayContaining([
+                { type: "text", text: "Describe this image." },
+                {
+                    type: "image_url",
+                    image_url: {
+                        url: "data:image/png;base64,aGVsbG8=",
+                    },
+                },
+            ]),
+        )
+    })
+})