1 files changed, 118 insertions, 0 deletions
diff --git a/src/internal/coverage/cmerge/merge_test.go b/src/internal/coverage/cmerge/merge_test.go
new file mode 100644
index 0000000..0e6112a
--- /dev/null
+++ b/src/internal/coverage/cmerge/merge_test.go
@@ -0,0 +1,118 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cmerge_test
+
+import (
+	"fmt"
+	"internal/coverage"
+	"internal/coverage/cmerge"
+	"testing"
+)
+
+func TestClash(t *testing.T) {
+	m := &cmerge.Merger{}
+	err := m.SetModeAndGranularity("mdf1.data", coverage.CtrModeSet, coverage.CtrGranularityPerBlock)
+	if err != nil {
+		t.Fatalf("unexpected clash: %v", err)
+	}
+	err = m.SetModeAndGranularity("mdf1.data", coverage.CtrModeSet, coverage.CtrGranularityPerBlock)
+	if err != nil {
+		t.Fatalf("unexpected clash: %v", err)
+	}
+	err = m.SetModeAndGranularity("mdf1.data", coverage.CtrModeCount, coverage.CtrGranularityPerBlock)
+	if err == nil {
+		t.Fatalf("expected mode clash, not found")
+	}
+	err = m.SetModeAndGranularity("mdf1.data", coverage.CtrModeSet, coverage.CtrGranularityPerFunc)
+	if err == nil {
+		t.Fatalf("expected granularity clash, not found")
+	}
+	m.SetModeMergePolicy(cmerge.ModeMergeRelaxed)
+	err = m.SetModeAndGranularity("mdf1.data", coverage.CtrModeCount, coverage.CtrGranularityPerBlock)
+	if err != nil {
+		t.Fatalf("unexpected clash: %v", err)
+	}
+	err = m.SetModeAndGranularity("mdf1.data", coverage.CtrModeSet, coverage.CtrGranularityPerBlock)
+	if err != nil {
+		t.Fatalf("unexpected clash: %v", err)
+	}
+	err = m.SetModeAndGranularity("mdf1.data", coverage.CtrModeAtomic, coverage.CtrGranularityPerBlock)
+	if err != nil {
+		t.Fatalf("unexpected clash: %v", err)
+	}
+	m.ResetModeAndGranularity()
+	err = m.SetModeAndGranularity("mdf1.data", coverage.CtrModeCount, coverage.CtrGranularityPerFunc)
+	if err != nil {
+		t.Fatalf("unexpected clash after reset: %v", err)
+	}
+}
+
+func TestBasic(t *testing.T) {
+	scenarios := []struct {
+		cmode         coverage.CounterMode
+		cgran         coverage.CounterGranularity
+		src, dst, res []uint32
+		iters         int
+		merr          bool
+		overflow      bool
+	}{
+		{
+			cmode:    coverage.CtrModeSet,
+			cgran:    coverage.CtrGranularityPerBlock,
+			src:      []uint32{1, 0, 1},
+			dst:      []uint32{1, 1, 0},
+			res:      []uint32{1, 1, 1},
+			iters:    2,
+			overflow: false,
+		},
+		{
+			cmode:    coverage.CtrModeCount,
+			cgran:    coverage.CtrGranularityPerBlock,
+			src:      []uint32{1, 0, 3},
+			dst:      []uint32{5, 7, 0},
+			res:      []uint32{6, 7, 3},
+			iters:    1,
+			overflow: false,
+		},
+		{
+			cmode:    coverage.CtrModeCount,
+			cgran:    coverage.CtrGranularityPerBlock,
+			src:      []uint32{4294967200, 0, 3},
+			dst:      []uint32{4294967001, 7, 0},
+			res:      []uint32{4294967295, 7, 3},
+			iters:    1,
+			overflow: true,
+		},
+	}
+
+	for k, scenario := range scenarios {
+		var err error
+		var ovf bool
+		m := &cmerge.Merger{}
+		mdf := fmt.Sprintf("file%d", k)
+		err = m.SetModeAndGranularity(mdf, scenario.cmode, scenario.cgran)
+		if err != nil {
+			t.Fatalf("case %d SetModeAndGranularity failed: %v", k, err)
+		}
+		for i := 0; i < scenario.iters; i++ {
+			err, ovf = m.MergeCounters(scenario.dst, scenario.src)
+			if ovf != scenario.overflow {
+				t.Fatalf("case %d overflow mismatch: got %v want %v", k, ovf, scenario.overflow)
+			}
+			if !scenario.merr && err != nil {
+				t.Fatalf("case %d unexpected err %v", k, err)
+			}
+			if scenario.merr && err == nil {
+				t.Fatalf("case %d expected err, not received", k)
+			}
+			for i := range scenario.dst {
+				if scenario.dst[i] != scenario.res[i] {
+					t.Fatalf("case %d: bad merge at %d got %d want %d",
+						k, i, scenario.dst[i], scenario.res[i])
+				}
+			}
+		}
+	}
+}