github.com/rck/u-root@v0.0.0-20180106144920-7eb602e381bb/cmds/tail/tail_test.go (about)

     1  package main
     2  
     3  import (
     4  	"bytes"
     5  	"io"
     6  	"os"
     7  	"testing"
     8  )
     9  
    10  func TestTailReadBackwards(t *testing.T) {
    11  	input, err := os.Open("./test_samples/read_backwards.txt")
    12  	if err != nil {
    13  		t.Error(err)
    14  	}
    15  	output := &bytes.Buffer{}
    16  	err = readLastLinesBackwards(input, output, 2)
    17  	if err != nil {
    18  		t.Error(err)
    19  	}
    20  	expected := []byte("second\nthird\n")
    21  	got := output.Bytes()
    22  	if !bytes.Equal(got, expected) {
    23  		t.Fatalf("Invalid result reading backwards. Got %v; want %v", got, expected)
    24  	}
    25  	// try reading more, which should return EOF
    26  	buf := make([]byte, 16)
    27  	n, err := input.Read(buf)
    28  	if err == nil {
    29  		t.Fatalf("Expected EOF, got more bytes instead: %v", string(buf[:n]))
    30  	}
    31  	if err != io.EOF {
    32  		t.Fatalf("Expected EOF, got another error instead: %v", err)
    33  	}
    34  }
    35  
    36  func TestTailReadFromBeginning(t *testing.T) {
    37  	input, err := os.Open("./test_samples/read_from_beginning.txt")
    38  	if err != nil {
    39  		t.Error(err)
    40  	}
    41  	output := &bytes.Buffer{}
    42  	err = readLastLinesFromBeginning(input, output, 3)
    43  	if err != nil {
    44  		t.Error(err)
    45  	}
    46  	expected := []byte("eight\nnine\nten\n")
    47  	got := make([]byte, 4096) // anything larger than the expected result
    48  	n, err := output.Read(got)
    49  	if err != nil {
    50  		t.Fatal(err)
    51  	}
    52  	if !bytes.Equal(got[:n], expected) {
    53  		t.Fatalf("Invalid data while reading from the beginning. Got %v; want %v", string(got[:n]), string(expected))
    54  	}
    55  	// try reading more, which should return EOF
    56  	buf := make([]byte, 16)
    57  	n, err = input.Read(buf)
    58  	if err == nil {
    59  		t.Fatalf("Expected EOF, got more bytes instead: %v", string(buf[:n]))
    60  	}
    61  	if err != io.EOF {
    62  		t.Fatalf("Expected EOF, got another error instead: %v", err)
    63  	}
    64  }