[1/4] support/testing/tests/package/test_compressor_base.py: new helper class

diff --git a/DEVELOPERS b/DEVELOPERS
index 188c579010..75cfbd85a8 100644
--- a/DEVELOPERS
+++ b/DEVELOPERS
@@ -1721,6 +1721,7 @@  F:	support/testing/tests/package/sample_python_gnupg.py
 F:	support/testing/tests/package/sample_python_hwdata.py
 F:	support/testing/tests/package/sample_python_pyalsa.py
 F:	support/testing/tests/package/sample_python_spake2.py
+F:	support/testing/tests/package/test_compressor_base.py
 F:	support/testing/tests/package/test_ddrescue.py
 F:	support/testing/tests/package/test_ddrescue/
 F:	support/testing/tests/package/test_gnupg2.py
diff --git a/support/testing/tests/package/test_compressor_base.py b/support/testing/tests/package/test_compressor_base.py
new file mode 100644
index 0000000000..6555584c10
--- /dev/null
+++ b/support/testing/tests/package/test_compressor_base.py
@@ -0,0 +1,126 @@ 
+import os
+
+import infra.basetest
+
+
+class TestCompressorBase(infra.basetest.BRTest):
+    """Common class to test a data compression/decompression package.
+
+    Build an image containing the package enabled in config, start the
+    emulator, login to it. It prepares a test data file with some
+    redundancy to let compression program reduce the file size.
+
+    Each test case that inherits from this class must have:
+    __test__ = True  - to let nose2 know that it is a test case
+    config           - defconfig fragment with the packages to run the test
+    compress_cmd     - the compression program command (ex: "gzip")
+                       it can also contain arguments (ex: "gzip -9")
+    It also can have:
+    decompress_cmd   - the decompression program (ex: "gunzip")
+                       if unset, the default value is "un" appended with the
+                       value of "compress_cmd".
+    check_integrity_cmd
+                     - the integrity check command (ex: "gzip -t")
+                       in unset, the default value is "compress_cmd" appended
+                       with " -t".
+    compressed_file_ext
+                     - the file extention of compressed files created by the
+                       compress command. (ex: ".gz")
+                       if unset, the default value is a dot "." appended with
+                       the value of "compress_cmd".
+    timeout          - timeout to the compression command. Some compression
+                       program can take more time than the default value
+                       (set to 5 seconds).
+    """
+    __test__ = False
+    config = infra.basetest.BASIC_TOOLCHAIN_CONFIG + \
+        """
+        BR2_TARGET_ROOTFS_CPIO=y
+        # BR2_TARGET_ROOTFS_TAR is not set
+        """
+    compress_cmd = "compressor-unknown"
+    decompress_cmd = None
+    check_integrity_cmd = None
+    compressed_file_ext = None
+    timeout = 5
+
+    def __init__(self, names):
+        """Setup common test variables."""
+        super(TestCompressorBase, self).__init__(names)
+
+        if self.decompress_cmd is None:
+            self.decompress_cmd = "un" + self.compress_cmd
+
+        if self.check_integrity_cmd is None:
+            self.check_integrity_cmd = self.compress_cmd + " -t"
+
+        if self.compressed_file_ext is None:
+            self.compressed_file_ext = "." + self.compress_cmd
+
+        self.ref_file = "reference.bin"
+        self.test_file = "test.bin"
+        self.comp_test_file = self.test_file + self.compressed_file_ext
+
+    def login(self):
+        cpio_file = os.path.join(self.builddir, "images", "rootfs.cpio")
+        self.emulator.boot(arch="armv5",
+                           kernel="builtin",
+                           options=["-initrd", cpio_file])
+        self.emulator.login()
+
+    def test_run(self):
+        self.login()
+        self.prepare_data()
+        self.compress_test()
+        self.check_integrity_test()
+        self.uncompress_test()
+        self.compare_test()
+
+    def prepare_data(self):
+        # Create a data file composed of: 128kB of random data, then
+        # 128kB of zeroes, then a repetition of the 1st 128kB of
+        # random.
+        self.assertRunOk("dd if=/dev/urandom of=rand.bin bs=128k count=1")
+        self.assertRunOk("dd if=/dev/zero of=zeroes.bin bs=128k count=1")
+        self.assertRunOk(f"cat rand.bin zeroes.bin rand.bin > {self.ref_file}")
+
+        # Keep a copy of the reference data since
+        # compressor/decompressor programs usually unlink source data
+        # file.
+        self.assertRunOk(f"cp {self.ref_file} {self.test_file}")
+
+    def compress_test(self):
+        # Run the compression
+        self.assertRunOk(f"{self.compress_cmd} {self.test_file}", timeout=self.timeout)
+
+        # Check that the compressed file was created with the expected name
+        self.assertRunOk(f"test -e {self.comp_test_file}")
+
+        # Remove the input test file. Some compressors (like gzip) are
+        # removing it automatically by default. Some others (like lz4)
+        # are keeping those by default. We always remove it to make
+        # sure a new file will be recreated by the decompression.
+        self.assertRunOk(f"rm -f {self.test_file}")
+
+        # Check the compressed file is smaller than the input.
+        # The "ls -l" command is for simplifying debugging
+        self.assertRunOk(f"ls -l {self.ref_file} {self.comp_test_file}")
+        ref_sz_cmd = f"wc -c < {self.ref_file}"
+        comp_sz_cmd = f"wc -c < {self.comp_test_file}"
+        self.assertRunOk(f"test $({ref_sz_cmd}) -gt $({comp_sz_cmd})")
+
+    def check_integrity_test(self):
+        # Check the compressed file integrity
+        self.assertRunOk(f"{self.check_integrity_cmd} {self.comp_test_file}")
+
+    def uncompress_test(self):
+        # Run the decompression
+        self.assertRunOk(f"{self.decompress_cmd} {self.comp_test_file}")
+
+        # Check the decompressed file was created with the correct name
+        self.assertRunOk(f"test -e {self.test_file}")
+
+    def compare_test(self):
+        # Check the decompressed file is exactly the same as the
+        # reference created at the beginning
+        self.assertRunOk(f"cmp {self.test_file} {self.ref_file}")