Test ContainerIO for correctness

Tests/test_file_container.py

@@ -3,6 +3,8 @@ from helper import unittest, PillowTestCase, hopper
 from PIL import Image
 from PIL import ContainerIO
 
+TEST_FILE = "Tests/images/dummy.container"
+
 
 class TestFileContainer(PillowTestCase):
 
@@ -16,6 +18,112 @@ class TestFileContainer(PillowTestCase):
 
         self.assertEqual(container.isatty(), 0)
 
+    def test_seek_mode_0(self):
+        # Arrange
+        mode = 0
+        with open(TEST_FILE) as fh:
+            container = ContainerIO.ContainerIO(fh, 22, 100)
+
+            # Act
+            container.seek(33, mode)
+            container.seek(33, mode)
+
+            # Assert
+            self.assertEqual(container.tell(), 33)
+
+    def test_seek_mode_1(self):
+        # Arrange
+        mode = 1
+        with open(TEST_FILE) as fh:
+            container = ContainerIO.ContainerIO(fh, 22, 100)
+
+            # Act
+            container.seek(33, mode)
+            container.seek(33, mode)
+
+            # Assert
+            self.assertEqual(container.tell(), 66)
+
+    def test_seek_mode_2(self):
+        # Arrange
+        mode = 2
+        with open(TEST_FILE) as fh:
+            container = ContainerIO.ContainerIO(fh, 22, 100)
+
+            # Act
+            container.seek(33, mode)
+            container.seek(33, mode)
+
+            # Assert
+            self.assertEqual(container.tell(), 100)
+
+    def test_read_n0(self):
+        # Arrange
+        with open(TEST_FILE) as fh:
+            container = ContainerIO.ContainerIO(fh, 22, 100)
+
+            # Act
+            container.seek(81)
+            data = container.read()
+
+            # Assert
+            self.assertEqual(data, "7\nThis is line 8\n")
+
+    def test_read_n(self):
+        # Arrange
+        with open(TEST_FILE) as fh:
+            container = ContainerIO.ContainerIO(fh, 22, 100)
+
+            # Act
+            container.seek(81)
+            data = container.read(3)
+
+            # Assert
+            self.assertEqual(data, "7\nT")
+
+    def test_read_eof(self):
+        # Arrange
+        with open(TEST_FILE) as fh:
+            container = ContainerIO.ContainerIO(fh, 22, 100)
+
+            # Act
+            container.seek(100)
+            data = container.read()
+
+            # Assert
+            self.assertEqual(data, "")
+
+    def test_readline(self):
+        # Arrange
+        with open(TEST_FILE) as fh:
+            container = ContainerIO.ContainerIO(fh, 0, 120)
+
+            # Act
+            data = container.readline()
+
+            # Assert
+            self.assertEqual(data, "This is line 1\n")
+
+    def test_readlines(self):
+        # Arrange
+        expected = ["This is line 1\n",
+                    "This is line 2\n",
+                    "This is line 3\n",
+                    "This is line 4\n",
+                    "This is line 5\n",
+                    "This is line 6\n",
+                    "This is line 7\n",
+                    "This is line 8\n"]
+        with open(TEST_FILE) as fh:
+            container = ContainerIO.ContainerIO(fh, 0, 120)
+
+            # Act
+            data = container.readlines()
+
+            # Assert
+
+            self.assertEqual(data, expected)
+
 
 if __name__ == '__main__':
     unittest.main()