github.com/mvdan/u-root-coreutils@v0.0.0-20230122170626-c2eef2898555/cmds/core/tail/tail_test.go (about)

     1  // Copyright 2018 the u-root Authors. All rights reserved
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package main
     6  
     7  import (
     8  	"bytes"
     9  	"io"
    10  	"os"
    11  	"testing"
    12  )
    13  
    14  func TestTailReadBackwards(t *testing.T) {
    15  	input, err := os.Open("./test_samples/read_backwards.txt")
    16  	if err != nil {
    17  		t.Error(err)
    18  	}
    19  	output := &bytes.Buffer{}
    20  	err = readLastLinesBackwards(input, output, 2)
    21  	if err != nil {
    22  		t.Error(err)
    23  	}
    24  	expected := []byte("second\nthird\n")
    25  	got := output.Bytes()
    26  	if !bytes.Equal(got, expected) {
    27  		t.Fatalf("Invalid result reading backwards. Got %v; want %v", got, expected)
    28  	}
    29  	// try reading more, which should return EOF
    30  	buf := make([]byte, 16)
    31  	n, err := input.Read(buf)
    32  	if err == nil {
    33  		t.Fatalf("Expected EOF, got more bytes instead: %v", string(buf[:n]))
    34  	}
    35  	if err != io.EOF {
    36  		t.Fatalf("Expected EOF, got another error instead: %v", err)
    37  	}
    38  }
    39  
    40  func TestTailReadFromBeginning(t *testing.T) {
    41  	input, err := os.Open("./test_samples/read_from_beginning.txt")
    42  	if err != nil {
    43  		t.Error(err)
    44  	}
    45  	output := &bytes.Buffer{}
    46  	err = readLastLinesFromBeginning(input, output, 3)
    47  	if err != nil {
    48  		t.Error(err)
    49  	}
    50  	expected := []byte("eight\nnine\nten\n")
    51  	got := make([]byte, 4096) // anything larger than the expected result
    52  	n, err := output.Read(got)
    53  	if err != nil {
    54  		t.Fatal(err)
    55  	}
    56  	if !bytes.Equal(got[:n], expected) {
    57  		t.Fatalf("Invalid data while reading from the beginning. Got %v; want %v", string(got[:n]), string(expected))
    58  	}
    59  	// try reading more, which should return EOF
    60  	buf := make([]byte, 16)
    61  	n, err = input.Read(buf)
    62  	if err == nil {
    63  		t.Fatalf("Expected EOF, got more bytes instead: %v", string(buf[:n]))
    64  	}
    65  	if err != io.EOF {
    66  		t.Fatalf("Expected EOF, got another error instead: %v", err)
    67  	}
    68  }
    69  
    70  func TestTailRun(t *testing.T) {
    71  	f, err := os.CreateTemp("", "tailRunTest")
    72  	if err != nil {
    73  		t.Fatal(err)
    74  	}
    75  	defer os.Remove(f.Name())
    76  
    77  	input := "a\nb\nc\n"
    78  	_, err = f.WriteString(input)
    79  	if err != nil {
    80  		t.Fatal(err)
    81  	}
    82  
    83  	var b bytes.Buffer
    84  	err = run(os.Stdin, &b, []string{f.Name()})
    85  	if err != nil {
    86  		t.Error(err)
    87  	}
    88  
    89  	if b.String() != input {
    90  		t.Errorf("tail output does not match, want %q, got %q", input, b.String())
    91  	}
    92  
    93  	err = run(nil, nil, []string{"a", "b"})
    94  	if err == nil {
    95  		t.Error("tail should return an error if more than one file specified")
    96  	}
    97  
    98  	b.Truncate(0)
    99  	*flagNumLines = -1
   100  	err = run(f, &b, nil)
   101  	if err != nil {
   102  		t.Error(err)
   103  	}
   104  
   105  	if b.String() != "c\n" {
   106  		t.Errorf("tail output does not match, want %q, got %q", input, b.String())
   107  	}
   108  }
   109  
   110  func TestLastNLines(t *testing.T) {
   111  	tests := []struct {
   112  		input  []byte
   113  		output []byte
   114  		n      uint
   115  	}{
   116  		{
   117  			input:  []byte{'a', '\n', '\n', 'b', '\n'},
   118  			output: []byte{'a', '\n', '\n', 'b', '\n'},
   119  			n:      4,
   120  		},
   121  		{
   122  			input:  []byte{'a', '\n', '\n', 'b', '\n'},
   123  			output: []byte{'a', '\n', '\n', 'b', '\n'},
   124  			n:      3,
   125  		},
   126  		{
   127  			input:  []byte{'a', '\n', '\n', 'b', '\n'},
   128  			output: []byte{'\n', 'b', '\n'},
   129  			n:      2,
   130  		},
   131  		{
   132  			input:  []byte{'a', '\n', '\n', 'b', '\n'},
   133  			output: []byte{'b', '\n'},
   134  			n:      1,
   135  		},
   136  		{
   137  			input:  []byte{'a', '\n', 'b', '\n', 'c', '\n'},
   138  			output: []byte{'c', '\n'},
   139  			n:      1,
   140  		},
   141  		{
   142  			input:  []byte{'a', '\n', 'b', '\n', 'c'},
   143  			output: []byte{'c'},
   144  			n:      1,
   145  		},
   146  		{
   147  			input:  []byte{'\n'},
   148  			output: []byte{'\n'},
   149  			n:      1,
   150  		},
   151  	}
   152  
   153  	for _, test := range tests {
   154  		r := lastNLines(test.input, test.n)
   155  		if !bytes.Equal(r, test.output) {
   156  			t.Errorf("want: %q, got: %q", string(test.output), string(r))
   157  		}
   158  	}
   159  }