Will Murphy
0253a76dbe
Previously, reading fragment 512 would panic with index out of range. Fix that panic by introducing an abstraction over reading blocks of items, caching the intermediate result, and returning an item at a particular index. The primary goal of this abstraction is to make edge cases like requesting items on page boundaries easy to unit test for. Additionally, fix unit tests by making t.Fatal calls protected by nil checks on the error values.
131 lines
3.4 KiB
Go
131 lines
3.4 KiB
Go
package squashfslow
|
|
|
|
import (
|
|
"errors"
|
|
"testing"
|
|
)
|
|
|
|
func requireNoError(t *testing.T, err error) {
|
|
t.Helper()
|
|
if err != nil {
|
|
t.Fatal(err)
|
|
}
|
|
}
|
|
|
|
func assertEqual(t *testing.T, want int, got int) {
|
|
t.Helper()
|
|
if want != got {
|
|
t.Errorf("want %d, got %d", want, got)
|
|
}
|
|
}
|
|
|
|
func assertLength(t *testing.T, want int, slice []int) {
|
|
t.Helper()
|
|
if len(slice) != want {
|
|
t.Errorf("want len %d, got %d", want, len(slice))
|
|
}
|
|
}
|
|
|
|
func assertErrorIs(t *testing.T, err error, wantErr error) {
|
|
t.Helper()
|
|
if err == nil {
|
|
t.Errorf("want %s, got nil", wantErr)
|
|
return
|
|
}
|
|
if !errors.Is(err, wantErr) {
|
|
t.Errorf("want %s, got %v", wantErr, err)
|
|
}
|
|
}
|
|
|
|
func TestCachingPagedReader(t *testing.T) {
|
|
// Mock readBlocks function
|
|
mockReadNMore := func(startBlock, numItems int) ([]int, error) {
|
|
if startBlock < 0 {
|
|
return nil, errors.New("invalid block start")
|
|
}
|
|
var result []int
|
|
for i := 0; i < numItems; i++ {
|
|
result = append(result, startBlock*512+i)
|
|
}
|
|
return result, nil
|
|
}
|
|
|
|
t.Run("ValidRequestWithinFirstBlock", func(t *testing.T) {
|
|
currentItems := make([]int, 0)
|
|
item, err := readPagedItems(300, 512, ¤tItems, 2048, mockReadNMore)
|
|
requireNoError(t, err)
|
|
assertEqual(t, 300, item)
|
|
assertLength(t, 512, currentItems) // Ensure one block is read
|
|
})
|
|
|
|
t.Run("ValidRequestAcrossMultipleBlocks", func(t *testing.T) {
|
|
currentItems := make([]int, 0)
|
|
item, err := readPagedItems(600, 512, ¤tItems, 2048, mockReadNMore)
|
|
requireNoError(t, err)
|
|
assertEqual(t, 600, item)
|
|
assertLength(t, 1024, currentItems)
|
|
})
|
|
|
|
t.Run("SequentialRequestsWithinBlocks", func(t *testing.T) {
|
|
currentItems := make([]int, 0)
|
|
// First request
|
|
item, err := readPagedItems(300, 512, ¤tItems, 2048, mockReadNMore)
|
|
requireNoError(t, err)
|
|
assertEqual(t, 300, item)
|
|
|
|
// Second request in the same block
|
|
item, err = readPagedItems(400, 512, ¤tItems, 2048, mockReadNMore)
|
|
requireNoError(t, err)
|
|
assertEqual(t, 400, item)
|
|
assertLength(t, 512, currentItems)
|
|
})
|
|
|
|
t.Run("RequestExactBlockBoundary", func(t *testing.T) {
|
|
currentItems := make([]int, 0)
|
|
item, err := readPagedItems(511, 512, ¤tItems, 2048, mockReadNMore)
|
|
requireNoError(t, err)
|
|
assertEqual(t, 511, item)
|
|
assertLength(t, 512, currentItems)
|
|
|
|
// Request the next block's first item
|
|
item, err = readPagedItems(512, 512, ¤tItems, 2048, mockReadNMore)
|
|
requireNoError(t, err)
|
|
assertEqual(t, 512, item)
|
|
assertLength(t, 1024, currentItems)
|
|
})
|
|
|
|
t.Run("OutOfBoundsRequest", func(t *testing.T) {
|
|
currentItems := make([]int, 0)
|
|
_, err := readPagedItems(2048, 512, ¤tItems, 2048, mockReadNMore)
|
|
assertErrorIs(t, err, errOutOfBounds)
|
|
})
|
|
|
|
t.Run("RequestBeyondReadBlocks", func(t *testing.T) {
|
|
readFail := errors.New("failed to read block")
|
|
failingReadBlocks := func(startBlock, numBlocks int) ([]int, error) {
|
|
if startBlock > 1 {
|
|
return nil, readFail
|
|
}
|
|
var result []int
|
|
for i := 0; i < numBlocks*512; i++ {
|
|
result = append(result, startBlock*512+i)
|
|
}
|
|
return result, nil
|
|
}
|
|
|
|
currentItems := make([]int, 0)
|
|
_, err := readPagedItems(1024, 512, ¤tItems, 2048, failingReadBlocks)
|
|
assertErrorIs(t, err, readFail)
|
|
})
|
|
|
|
t.Run("partial last page", func(t *testing.T) {
|
|
currentItems := make([]int, 0)
|
|
|
|
// Request the next block's first item
|
|
item, err := readPagedItems(512, 512, ¤tItems, 612, mockReadNMore)
|
|
requireNoError(t, err)
|
|
assertEqual(t, 512, item)
|
|
assertLength(t, 612, currentItems)
|
|
})
|
|
}
|