Add KJ-test macros for expecting exceptions and log messages.

c++/src/kj/test.c++

@@ -57,6 +57,41 @@ TestCase::~TestCase() {
 
 namespace _ {  // private
 
+bool hasSubstring(kj::StringPtr haystack, kj::StringPtr needle) {
+  // TODO(perf): This is not the best algorithm for substring matching.
+  for (size_t i = 0; i <= haystack.size() - needle.size(); i++) {
+    if (haystack.slice(i).startsWith(needle)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+LogExpectation::LogExpectation(LogSeverity severity, StringPtr substring)
+    : severity(severity), substring(substring), seen(false) {}
+LogExpectation::~LogExpectation() {
+  if (!unwindDetector.isUnwinding()) {
+    KJ_ASSERT(seen, "expected log message not seen", severity, substring);
+  }
+}
+
+void LogExpectation::logMessage(
+    LogSeverity severity, const char* file, int line, int contextDepth,
+    String&& text) {
+  if (!seen && severity == this->severity) {
+    if (hasSubstring(text, substring)) {
+      // Match. Ignore it.
+      seen = true;
+      return;
+    }
+  }
+
+  // Pass up the chain.
+  ExceptionCallback::logMessage(severity, file, line, contextDepth, kj::mv(text));
+}
+
+// =======================================================================================
+
 GlobFilter::GlobFilter(const char* pattern): pattern(heapString(pattern)) {}
 GlobFilter::GlobFilter(ArrayPtr<const char> pattern): pattern(heapString(pattern)) {}
 

c++/src/kj/test.h

@@ -73,10 +73,52 @@ private:
   if (cond); else KJ_FAIL_EXPECT("failed: expected " #cond, ##__VA_ARGS__)
 #endif
 
+#define KJ_EXPECT_THROW(type, code) \
+  do { \
+    KJ_IF_MAYBE(e, ::kj::runCatchingExceptions([&]() { code; })) { \
+      KJ_EXPECT(e->getType() == ::kj::Exception::Type::type, \
+          "code threw wrong exception type: " #code, e->getType()); \
+    } else { \
+      KJ_FAIL_EXPECT("code did not throw: " #code); \
+    } \
+  } while (false)
+
+#define KJ_EXPECT_THROW_MESSAGE(message, code) \
+  do { \
+    KJ_IF_MAYBE(e, ::kj::runCatchingExceptions([&]() { code; })) { \
+      KJ_EXPECT(::kj::_::hasSubstring(e->getDescription(), message), \
+          "exception description didn't contain expected substring", e->getDescription()); \
+    } else { \
+      KJ_FAIL_EXPECT("code did not throw: " #code); \
+    } \
+  } while (false)
+
+#define KJ_EXPECT_LOG(level, substring) \
+  ::kj::_::LogExpectation KJ_UNIQUE_NAME(_kjLogExpectation)(::kj::LogSeverity::level, substring)
+// Expects that a log message with the given level and substring text will be printed within
+// the current scope. This message will not cause the test to fail, even if it is an error.
+
 // =======================================================================================
 
 namespace _ {  // private
 
+bool hasSubstring(kj::StringPtr haystack, kj::StringPtr needle);
+
+class LogExpectation: public ExceptionCallback {
+public:
+  LogExpectation(LogSeverity severity, StringPtr substring);
+  ~LogExpectation();
+
+  void logMessage(LogSeverity severity, const char* file, int line, int contextDepth,
+                  String&& text) override;
+
+private:
+  LogSeverity severity;
+  StringPtr substring;
+  bool seen;
+  UnwindDetector unwindDetector;
+};
+
 class GlobFilter {
   // Implements glob filters for the --filter flag.
   //