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diff --git a/clang-tools-extra/unittests/clangd/QualityTests.cpp b/clang-tools-extra/unittests/clangd/QualityTests.cpp
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+++ b/clang-tools-extra/unittests/clangd/QualityTests.cpp
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+//===-- SourceCodeTests.cpp  ------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Evaluating scoring functions isn't a great fit for assert-based tests.
+// For interesting cases, both exact scores and "X beats Y" are too brittle to
+// make good hard assertions.
+//
+// Here we test the signal extraction and sanity-check that signals point in
+// the right direction. This should be supplemented by quality metrics which
+// we can compute from a corpus of queries and preferred rankings.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Quality.h"
+#include "TestTU.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace clang {
+namespace clangd {
+namespace {
+
+TEST(QualityTests, SymbolQualitySignalExtraction) {
+  auto Header = TestTU::withHeaderCode(R"cpp(
+    int x;
+
+    [[deprecated]]
+    int f() { return x; }
+  )cpp");
+  auto Symbols = Header.headerSymbols();
+  auto AST = Header.build();
+
+  SymbolQualitySignals Quality;
+  Quality.merge(findSymbol(Symbols, "x"));
+  EXPECT_FALSE(Quality.Deprecated);
+  EXPECT_EQ(Quality.SemaCCPriority, SymbolQualitySignals().SemaCCPriority);
+  EXPECT_EQ(Quality.References, SymbolQualitySignals().References);
+
+  Symbol F = findSymbol(Symbols, "f");
+  F.References = 24; // TestTU doesn't count references, so fake it.
+  Quality = {};
+  Quality.merge(F);
+  EXPECT_FALSE(Quality.Deprecated); // FIXME: Include deprecated bit in index.
+  EXPECT_EQ(Quality.SemaCCPriority, SymbolQualitySignals().SemaCCPriority);
+  EXPECT_EQ(Quality.References, 24u);
+
+  Quality = {};
+  Quality.merge(CodeCompletionResult(&findDecl(AST, "f"), /*Priority=*/42));
+  EXPECT_TRUE(Quality.Deprecated);
+  EXPECT_EQ(Quality.SemaCCPriority, 42u);
+  EXPECT_EQ(Quality.References, SymbolQualitySignals().References);
+}
+
+TEST(QualityTests, SymbolRelevanceSignalExtraction) {
+  auto AST = TestTU::withHeaderCode(R"cpp(
+    [[deprecated]]
+    int f() { return 0; }
+  )cpp")
+                 .build();
+
+  SymbolRelevanceSignals Relevance;
+  Relevance.merge(CodeCompletionResult(&findDecl(AST, "f"), /*Priority=*/42,
+                                       nullptr, false, /*Accessible=*/false));
+  EXPECT_EQ(Relevance.NameMatch, SymbolRelevanceSignals().NameMatch);
+  EXPECT_TRUE(Relevance.Forbidden);
+}
+
+// Do the signals move the scores in the direction we expect?
+TEST(QualityTests, SymbolQualitySignalsSanity) {
+  SymbolQualitySignals Default;
+  EXPECT_EQ(Default.evaluate(), 1);
+
+  SymbolQualitySignals Deprecated;
+  Deprecated.Deprecated = true;
+  EXPECT_LT(Deprecated.evaluate(), Default.evaluate());
+
+  SymbolQualitySignals WithReferences, ManyReferences;
+  WithReferences.References = 10;
+  ManyReferences.References = 1000;
+  EXPECT_GT(WithReferences.evaluate(), Default.evaluate());
+  EXPECT_GT(ManyReferences.evaluate(), WithReferences.evaluate());
+
+  SymbolQualitySignals LowPriority, HighPriority;
+  LowPriority.SemaCCPriority = 60;
+  HighPriority.SemaCCPriority = 20;
+  EXPECT_GT(HighPriority.evaluate(), Default.evaluate());
+  EXPECT_LT(LowPriority.evaluate(), Default.evaluate());
+}
+
+TEST(QualityTests, SymbolRelevanceSignalsSanity) {
+  SymbolRelevanceSignals Default;
+  EXPECT_EQ(Default.evaluate(), 1);
+
+  SymbolRelevanceSignals Forbidden;
+  Forbidden.Forbidden = true;
+  EXPECT_LT(Forbidden.evaluate(), Default.evaluate());
+
+  SymbolRelevanceSignals PoorNameMatch;
+  PoorNameMatch.NameMatch = 0.2;
+  EXPECT_LT(PoorNameMatch.evaluate(), Default.evaluate());
+}
+
+TEST(QualityTests, SortText) {
+  EXPECT_LT(sortText(std::numeric_limits<float>::infinity()), sortText(1000.2));
+  EXPECT_LT(sortText(1000.2), sortText(1));
+  EXPECT_LT(sortText(1), sortText(0.3));
+  EXPECT_LT(sortText(0.3), sortText(0));
+  EXPECT_LT(sortText(0), sortText(-10));
+  EXPECT_LT(sortText(-10), sortText(-std::numeric_limits<float>::infinity()));
+
+  EXPECT_LT(sortText(1, "z"), sortText(0, "a"));
+  EXPECT_LT(sortText(0, "a"), sortText(0, "z"));
+}
+
+} // namespace
+} // namespace clangd
+} // namespace clang