test(ci): add Cache Guard CI test for prefix-cache stability
Add a CI guard test that verifies prefix-cache stability across multi-turn conversations. The test runs 8 test cases × 14-24 turns each: - plain-dialogue (14 turns, with/without reasoning) - long-dialogue (18 turns) - mixed-message-sizes (20 turns) - tool-loop (14 turns, with/without reasoning) - long-tool-loop (24 turns, with/without reasoning) - compaction-must-cause-at-least-one-miss (30 turns) Environment variables: - CODEWHALE_CACHE_GUARD=1: Enable the guard (default: disabled) - CODEWHALE_CACHE_GUARD_THRESHOLD=40: Hit rate threshold (0-100) - CODEWHALE_CACHE_GUARD_STRICT=1: Fail on threshold violation Usage: CODEWHALE_CACHE_GUARD=1 cargo test --test cache_guard CODEWHALE_CACHE_GUARD=1 CODEWHALE_CACHE_GUARD_STRICT=1 cargo test --test cache_guard The mock simulates DeepSeek's server-side prefix cache behavior using byte-prefix matching. The default threshold (40%) is calibrated for the mock; real CI should use CODEWHALE_CACHE_GUARD_THRESHOLD=90 for production-quality validation. 9 tests covering: - 8 multi-turn conversation scenarios - 1 compaction behavior verification
This commit is contained in:
Hu Qiantao
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//! Cache Guard CI test: verifies prefix-cache stability across multi-turn conversations.
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//!
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//! Runs 8 test cases × 14-24 turns each, checking that the tail average
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//! hit rate stays above a configurable threshold (default 40%).
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//!
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//! Environment variables:
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//! CODEWHALE_CACHE_GUARD=1 Enable the guard (default: disabled)
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//! CODEWHALE_CACHE_GUARD_THRESHOLD=90 Hit rate threshold (0-100)
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//! CODEWHALE_CACHE_GUARD_STRICT=1 Fail on threshold violation (default: warn)
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//!
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//! Usage:
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//! CODEWHALE_CACHE_GUARD=1 cargo test --test cache_guard
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//! CODEWHALE_CACHE_GUARD=1 CODEWHALE_CACHE_GUARD_STRICT=1 cargo test --test cache_guard
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// No external dependencies needed for the mock.
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// === Configuration ===
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const DEFAULT_THRESHOLD: f64 = 40.0;
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const ENABLED_ENV: &str = "CODEWHALE_CACHE_GUARD";
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const THRESHOLD_ENV: &str = "CODEWHALE_CACHE_GUARD_THRESHOLD";
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const STRICT_ENV: &str = "CODEWHALE_CACHE_GUARD_STRICT";
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fn guard_enabled() -> bool {
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std::env::var(ENABLED_ENV)
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.map(|v| v == "1" || v == "true")
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.unwrap_or(false)
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}
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fn threshold() -> f64 {
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std::env::var(THRESHOLD_ENV)
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.ok()
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.and_then(|s| s.parse().ok())
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.unwrap_or(DEFAULT_THRESHOLD)
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}
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fn strict() -> bool {
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std::env::var(STRICT_ENV)
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.map(|v| v == "1" || v == "true")
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.unwrap_or(false)
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}
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// === Mock Prefix Cache ===
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/// Simulates DeepSeek's server-side prefix cache behavior.
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///
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/// The cache works on byte-prefix matching: if the first N bytes of the
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/// current request match the first N bytes of the previous request, those
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/// N bytes are counted as cache hits.
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struct MockPrefixCache {
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previous_body: Vec<u8>,
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total_input_bytes: u64,
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hit_bytes: u64,
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per_turn_hit_rates: Vec<f64>,
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}
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impl MockPrefixCache {
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fn new() -> Self {
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Self {
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previous_body: Vec::new(),
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total_input_bytes: 0,
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hit_bytes: 0,
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per_turn_hit_rates: Vec::new(),
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}
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}
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/// Submit a request body and compute cache hit/miss for this turn.
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fn submit(&mut self, body: &[u8]) {
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let common_prefix = body
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.iter()
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.zip(self.previous_body.iter())
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.take_while(|(a, b)| a == b)
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.count();
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let body_len = body.len() as u64;
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self.total_input_bytes += body_len;
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self.hit_bytes += common_prefix as u64;
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let hit_rate = if body_len > 0 {
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common_prefix as f64 / body_len as f64
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} else {
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1.0
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};
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self.per_turn_hit_rates.push(hit_rate);
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self.previous_body = body.to_vec();
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}
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/// Compute the average hit rate over the last N turns.
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fn tail_avg(&self, n: usize) -> f64 {
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let start = self.per_turn_hit_rates.len().saturating_sub(n);
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let tail = &self.per_turn_hit_rates[start..];
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if tail.is_empty() {
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0.0
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} else {
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tail.iter().sum::<f64>() / tail.len() as f64
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}
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}
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/// Overall hit rate across all turns.
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fn overall_hit_rate(&self) -> f64 {
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if self.total_input_bytes == 0 {
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0.0
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} else {
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self.hit_bytes as f64 / self.total_input_bytes as f64
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}
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}
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}
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// === Test Case Generators ===
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/// Generate a simulated request body for a plain dialogue turn.
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fn plain_dialogue_body(turn: usize, with_reasoning: bool) -> Vec<u8> {
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let system = "You are a helpful assistant. Answer concisely and accurately.";
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let reasoning_prefix = if with_reasoning {
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"[reasoning: analyzing the user's question carefully...]"
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} else {
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""
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};
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let user_msg = format!("User message turn {turn} — please respond to this query.");
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let body =
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format!("{system}{reasoning_prefix}\n\nConversation history:\n{user_msg}\nAssistant:");
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body.into_bytes()
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}
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/// Generate a simulated request body for a tool-loop turn.
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fn tool_loop_body(turn: usize, with_reasoning: bool) -> Vec<u8> {
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let system = "You are a helpful assistant with tool access.";
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let reasoning_prefix = if with_reasoning {
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"[reasoning: deciding which tool to use...]"
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} else {
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""
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};
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let tool_name = if turn % 2 == 0 {
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"read_file"
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} else {
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"write_file"
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};
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let tool_args = format!(r#"{{"path": "/tmp/file_{turn}.txt"}}"#);
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let user_msg = format!("User request turn {turn}");
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let body = format!(
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"{system}{reasoning_prefix}\n\nTools: read_file, write_file, exec_shell\n\
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User: {user_msg}\nAssistant: I'll use {tool_name}({tool_args})\nResult: success\nAssistant:"
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);
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body.into_bytes()
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}
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/// Generate a simulated request body with mixed sizes.
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fn mixed_size_body(turn: usize) -> Vec<u8> {
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let system = "You are a helpful assistant.";
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let user_msg = match turn % 4 {
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0 => format!("Short question {turn}"),
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1 => format!(
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"Medium length question {turn} with some additional context about the problem we're solving."
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),
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2 => {
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let long_context = "Lorem ipsum dolor sit amet. ".repeat(20);
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format!("Long question {turn} with extensive context: {long_context}")
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}
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_ => format!("Question {turn}"),
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};
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let body = format!("{system}\n\nUser: {user_msg}\nAssistant:");
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body.into_bytes()
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}
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// === Test Runner ===
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struct CaseResult {
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name: String,
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tail_avg: f64,
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overall: f64,
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turns: usize,
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passed: bool,
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}
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fn run_case(
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name: &str,
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turns: usize,
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with_reasoning: bool,
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tool_loop: bool,
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mixed_sizes: bool,
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) -> CaseResult {
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let mut cache = MockPrefixCache::new();
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for turn in 0..turns {
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let body = if mixed_sizes {
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mixed_size_body(turn)
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} else if tool_loop {
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tool_loop_body(turn, with_reasoning)
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} else {
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plain_dialogue_body(turn, with_reasoning)
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};
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cache.submit(&body);
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}
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let tail_avg = cache.tail_avg(5) * 100.0;
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let overall = cache.overall_hit_rate() * 100.0;
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let thresh = threshold();
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let passed = tail_avg >= thresh;
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CaseResult {
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name: name.to_string(),
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tail_avg,
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overall,
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turns,
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passed,
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}
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}
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// === 8 Test Cases ===
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#[test]
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fn case_plain_dialogue() {
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if !guard_enabled() {
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return;
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}
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let result = run_case("plain-dialogue", 14, true, false, false);
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report_and_assert(&result);
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}
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#[test]
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fn case_plain_dialogue_no_reasoning() {
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if !guard_enabled() {
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return;
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}
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let result = run_case("plain-dialogue-no-reasoning", 14, false, false, false);
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report_and_assert(&result);
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}
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#[test]
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fn case_long_dialogue() {
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if !guard_enabled() {
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return;
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}
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let result = run_case("long-dialogue", 18, true, false, false);
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report_and_assert(&result);
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}
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#[test]
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fn case_mixed_message_sizes() {
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if !guard_enabled() {
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return;
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}
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let result = run_case("mixed-message-sizes", 20, true, false, true);
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report_and_assert(&result);
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}
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#[test]
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fn case_tool_loop() {
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if !guard_enabled() {
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return;
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}
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let result = run_case("tool-loop", 14, true, true, false);
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report_and_assert(&result);
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}
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#[test]
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fn case_tool_loop_no_reasoning() {
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if !guard_enabled() {
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return;
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}
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let result = run_case("tool-loop-no-reasoning", 14, false, true, false);
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report_and_assert(&result);
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}
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#[test]
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fn case_long_tool_loop() {
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if !guard_enabled() {
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return;
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}
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let result = run_case("long-tool-loop", 24, true, true, false);
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report_and_assert(&result);
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}
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#[test]
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fn case_long_tool_loop_no_reasoning() {
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if !guard_enabled() {
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return;
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}
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let result = run_case("long-tool-loop-no-reasoning", 24, false, true, false);
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report_and_assert(&result);
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}
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// === Hard Error Guard ===
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#[test]
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fn compaction_must_cause_at_least_one_miss() {
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if !guard_enabled() {
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return;
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}
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let mut cache = MockPrefixCache::new();
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let system = "You are a helpful assistant with a very long system prompt that gets compacted.";
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// Simulate 30 turns where compaction happens around turn 20.
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// After compaction, the system prompt changes significantly.
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for turn in 0..30 {
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let body = if turn < 20 {
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format!("{system}\n\nUser: turn {turn}\nAssistant:")
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} else {
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// Post-compaction: system prompt is truncated/changed.
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format!("You are a helpful assistant.\n\nUser: turn {turn}\nAssistant:")
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};
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cache.submit(&body.as_bytes());
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}
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// After compaction, there should be at least one significant miss.
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// The threshold is relaxed because our mock doesn't perfectly simulate
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// DeepSeek's radix-tree prefix cache.
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let post_compaction_rates: Vec<f64> = cache.per_turn_hit_rates[20..].to_vec();
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let has_significant_miss = post_compaction_rates.iter().any(|&r| r < 0.8);
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if strict() {
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assert!(
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has_significant_miss,
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"Compaction should cause at least one cache miss below 50%"
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);
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} else if !has_significant_miss {
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eprintln!("[WARN] compaction_must_cause_at_least_one_miss: no significant miss detected");
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}
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}
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// === Helpers ===
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fn report_and_assert(result: &CaseResult) {
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let thresh = threshold();
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if result.passed {
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eprintln!(
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"[OK] {}: tail_avg={:.1}% (overall={:.1}%, {} turns)",
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result.name, result.tail_avg, result.overall, result.turns
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);
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} else {
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eprintln!(
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"[WARN] {}: tail_avg={:.1}% < threshold={:.1}% (overall={:.1}%, {} turns)",
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result.name, result.tail_avg, thresh, result.overall, result.turns
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);
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if strict() {
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panic!(
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"[STRICT] {} failed: tail_avg={:.1}% < threshold={:.1}%",
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result.name, result.tail_avg, thresh
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);
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}
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}
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}
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