spring-ai/llm-gateway/src/test/java/com/ankurm/gateway/HttpTest.java

package com.ankurm.gateway;

import static org.assertj.core.api.Assertions.assertThat;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

import com.ankurm.gateway.support.FakeVendors;
import com.ankurm.gateway.support.Transcript;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.server.LocalServerPort;
import org.springframework.test.context.DynamicPropertyRegistry;
import org.springframework.test.context.DynamicPropertySource;

/** The whole application over HTTP: real beans, real models, a fake at the far end. */
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
class HttpTest {

    static final FakeVendors VENDORS;

    static {
        try {
            VENDORS = new FakeVendors();
        }
        catch (java.io.IOException e) {
            throw new ExceptionInInitializerError(e);
        }
    }

    @DynamicPropertySource
    static void providers(DynamicPropertyRegistry r) {
        r.add("gateway.providers[0].name", () -> "openai");
        r.add("gateway.providers[0].type", () -> "openai");
        r.add("gateway.providers[0].base-url", () -> VENDORS.url() + "/v1");
        r.add("gateway.providers[0].api-key", () -> "test-key");
        r.add("gateway.providers[0].model", () -> "gpt-6.1-sol");
        r.add("gateway.providers[0].input-price", () -> "2.00");
        r.add("gateway.providers[0].output-price", () -> "10.00");
        r.add("gateway.providers[1].name", () -> "anthropic");
        r.add("gateway.providers[1].type", () -> "anthropic");
        r.add("gateway.providers[1].base-url", () -> VENDORS.url());
        r.add("gateway.providers[1].api-key", () -> "test-key");
        r.add("gateway.providers[1].model", () -> "claude-sonnet-5-5");
        r.add("gateway.providers[1].input-price", () -> "2.00");
        r.add("gateway.providers[1].output-price", () -> "10.00");
        r.add("gateway.tenants.poor.budget-micros", () -> "1000");
        r.add("gateway.tenants.poor.tokens-per-hour", () -> "100000");
    }

    @LocalServerPort
    int port;

    private final HttpClient http = HttpClient.newHttpClient();

    @BeforeEach
    void reset() {
        VENDORS.openai.reset();
        VENDORS.anthropic.reset();
    }

    @AfterAll
    static void stop() {
        VENDORS.close();
    }

    private HttpResponse<String> post(String tenant, String json) throws Exception {
        HttpRequest.Builder b = HttpRequest.newBuilder(URI.create("http://127.0.0.1:" + port + "/v1/gateway/complete"))
                .header("Content-Type", "application/json").POST(HttpRequest.BodyPublishers.ofString(json));
        if (tenant != null) {
            b.header("X-Tenant-Id", tenant);
        }
        return http.send(b.build(), HttpResponse.BodyHandlers.ofString());
    }

    private static String body(String hint, String extra) {
        return "{\"featureTag\":\"support\",\"userMessage\":\"What is your return policy?\",\"modelHint\":\"" + hint
                + "\",\"maxTokens\":256" + extra + "}";
    }

    @Test
    void statusCodesAndBodiesOverHttp() throws Exception {
        try (Transcript t = new Transcript("10-http.txt", "The gateway over HTTP (real beans, real models, fake vendors)")) {
            VENDORS.openai.then(200, FakeVendors.openaiText("30 days.", 47, 52));
            HttpResponse<String> ok = post("acme", body("smart", ""));
            t.line("1. normal call            -> %d %s", ok.statusCode(), ok.body());
            assertThat(ok.statusCode()).isEqualTo(200);
            assertThat(ok.body()).contains("\"provider\":\"openai\"").contains("\"costMicros\":614");

            reset();
            VENDORS.openai.then(503, FakeVendors.error("server_error", "overloaded"));
            VENDORS.anthropic.then(200, FakeVendors.anthropicText("30 days.", 47, 52));
            HttpResponse<String> failover = post("acme", body("smart", ""));
            t.line("2. openai returns 503     -> %d %s", failover.statusCode(), failover.body());
            assertThat(failover.body()).contains("\"provider\":\"anthropic\"");

            reset();
            VENDORS.openai.always(503, FakeVendors.error("server_error", "overloaded"));
            VENDORS.anthropic.always(529, FakeVendors.error("overloaded_error", "overloaded"));
            HttpResponse<String> down = post("acme", body("smart", ""));
            t.line("3. both providers down    -> %d Retry-After=%s %s", down.statusCode(),
                    down.headers().firstValue("Retry-After").orElse("-"), down.body());
            assertThat(down.statusCode()).isEqualTo(503);

            reset();
            HttpResponse<String> hint = post("acme", body("locla", ""));
            t.line("4. unknown hint           -> %d %s", hint.statusCode(), hint.body());
            assertThat(hint.statusCode()).isEqualTo(400);
            assertThat(VENDORS.openai.requests() + VENDORS.anthropic.requests()).isZero();

            HttpResponse<String> tool = post("acme", body("smart", ",\"tools\":[\"drop_tables\"]"));
            t.line("5. tool not allow-listed  -> %d %s", tool.statusCode(), tool.body());
            assertThat(tool.statusCode()).isEqualTo(400);

            HttpResponse<String> poor = post("poor", body("smart", ""));
            t.line("6. tenant over its cap    -> %d %s", poor.statusCode(), poor.body());
            assertThat(poor.statusCode()).isEqualTo(429);
            assertThat(VENDORS.openai.requests() + VENDORS.anthropic.requests()).isZero();

            HttpResponse<String> spoof = post("poor", body("smart", ",\"tenantId\":\"acme\""));
            t.line("7. body claims tenant acme, header says poor -> %d (the header wins)", spoof.statusCode());
            assertThat(spoof.statusCode()).isEqualTo(429);

            HttpResponse<String> none = post(null, body("smart", ""));
            t.line("8. no X-Tenant-Id header  -> %d", none.statusCode());
            assertThat(none.statusCode()).isEqualTo(400);
        }
    }
}