schemadiff: adding a FK dependency unit test (#16069)

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

go/vt/schemadiff/schema_diff_test.go

@@ -979,6 +979,22 @@ func TestSchemaDiff(t *testing.T) {
  conflictingDiffs: 2,
  instantCapability: InstantDDLCapabilityImpossible,
  },
+ {
+ name: "add and drop FK, add and drop respective tables",
+ fromQueries: []string{
+ "create table t1 (id int primary key, p int, key p_idx (p));",
+ "create table t2 (id int primary key, p int, key p_idx (p), foreign key (p) references t1 (p) on delete no action);",
+ },
+ toQueries: []string{
+ "create table t2 (id int primary key, p int, key p_idx (p), foreign key (p) references t3 (p) on delete no action);",
+ "create table t3 (id int primary key, p int, key p_idx (p));",
+ },
+ expectDiffs: 3,
+ expectDeps: 2, // [alter t2]/[drop t1], [alter t2]/[create t3]
+ sequential: true,
+ entityOrder: []string{"t3", "t2", "t1"},
+ instantCapability: InstantDDLCapabilityImpossible,
+ },
  {
  name: "two identical foreign keys in table, drop one",
  fromQueries: []string{
@@ -1053,7 +1069,7 @@ func TestSchemaDiff(t *testing.T) {
  for _, dep := range deps {
  depsKeys = append(depsKeys, dep.hashKey())
  }
- assert.Equalf(t, tc.expectDeps, len(deps), "found deps: %v", depsKeys)
+ assert.Equalf(t, tc.expectDeps, len(deps), "found %v deps: %v", len(depsKeys), depsKeys)
  assert.Equal(t, tc.sequential, schemaDiff.HasSequentialExecutionDependencies())
 
  orderedDiffs, err := schemaDiff.OrderedDiffs(ctx)