.

wcfs/internal/zdata/δftail_test.go

@@ -29,7 +29,7 @@ package zdata
 //
 // Since ΔFtail does not recompute anything by itself when tracking set
 // changes, and only merges δBtail and δZtail histories on queries, there is no
-// need to exercise many different tracking sets. Once again we assume that
+// need to exercise many different tracking sets(*). Once again we assume that
 // ΔBtail works correctly and verify δFtail only with track=[-∞,∞).
 //
 // There are 2 testing approaches:
@@ -40,6 +40,9 @@ package zdata
 //      states and feed ΔFtail through created database transactions.
 //
 // TestΔFtail and TestΔFtailRandom implement approaches "a" and "b" correspondingly.
+//
+// (*) except one small place in SliceByFileRev which handles tracked vs
+//     untracked set differences and is verified by TestΔFtailSliceUntrackedUniform.
 
 import (
 	"context"
@@ -604,8 +607,17 @@ func testΔFtail(t_ *testing.T, testq chan ΔFTestEntry) {
 	}
 }
 
-// TestΔFtailXXX XXX.
-func TestΔFtailSliceXXX(t_ *testing.T) {
+// TestΔFtailSliceUntrackedUniform verifies that untracked blocks, if present, are present uniformly in returned slice.
+//
+// Some changes to untracked blocks, might be seen by ΔFtail, because those
+// changes occur in the same BTree bucket that covers another change to a
+// tracked block.
+//
+// Here we verify that if some change to such untracked block is ever present,
+// SliceByFileRev returns all changes to that untracked block. In other words
+// we verify that no change to untracked block is missed, if any change to that
+// block is ever present in returned slice.
+func TestΔFtailSliceUntrackedUniform(t_ *testing.T) {
 	t := xbtreetest.NewT(t_)
 	X := exc.Raiseif
 
@@ -614,6 +626,7 @@ func TestΔFtailSliceXXX(t_ *testing.T) {
 	xat[at0] = "at0"
 	δFtail := NewΔFtail(at0, t.DB)
 
+	// commit t1. 0 and 1 are in the same bucket.
 	t1 := t.CommitTree("T/B0:a,1:b")
 	xat[t1.At] = "at1"
 	δF, err := δFtail.Update(t1.ΔZ);  X(err)
@@ -668,21 +681,29 @@ func TestΔFtailSliceXXX(t_ *testing.T) {
 		return fmt.Sprintf("%s", s)
 	}
 
-	// XXX explain
+	// track 1, but do not track 0.
+	// blktab[0] becomes tracked by δBtail because both 0 and 1 are in the same bucket.
 	xtrackBlk(1)
 
-	t2 := t.CommitTree("t0:a,1:c Da:aa,b:b,c:c") // 1 -b+c, δa
+	t2 := t.CommitTree("t0:a,1:c Da:a2,b:b,c:c") // 1: -b+c, δa₂
 	xat[t2.At] = "at2"
 	δF, err = δFtail.Update(t2.ΔZ);  X(err)
+	// XXX assert δF
+
+	t3 := t.CommitTree("t0:a,1:c Da:a3,b:b,c:c") // δa₃
+	xat[t3.At] = "at3"
+	δF, err = δFtail.Update(t3.ΔZ);  X(err)
+	// XXX assert δF
 
 
 	lo := at0
-	hi := t2.At
+	hi := t3.At
 	vδf := δFtail.SliceByFileRev(zfile, lo, hi)
 	_01 := setI64{}; _01.Add(0); _01.Add(1)
 	vδf_ok := []*ΔFile{
 		&ΔFile{Rev: t1.At, Blocks: _01, Size: true},
 		&ΔFile{Rev: t2.At, Blocks: _01, Size: true},
+		&ΔFile{Rev: t3.At, Blocks: _01, Size: false},
 	}
 
 	if !reflect.DeepEqual(vδf, vδf_ok) {