diff --git a/src/DAJIN2/preprocess/validate_inputs.py b/src/DAJIN2/preprocess/validate_inputs.py
index 40e0040b..1a2a0566 100644
--- a/src/DAJIN2/preprocess/validate_inputs.py
+++ b/src/DAJIN2/preprocess/validate_inputs.py
@@ -5,62 +5,59 @@
 from pathlib import Path
 from urllib.error import URLError
 from urllib.request import urlopen
+import xml.etree.ElementTree as ET
 
 import mappy
 
 
-def _exist_file(input_file: str):
-    if not Path(input_file).exists():
-        raise FileNotFoundError(f"{input_file} is not found")
-
-
 ########################################################################
 # Check if the sample is in the proper format.
 ########################################################################
 
 
-def _fastq_extension(fastq_path: str):
+def _validate_file_existence(input_file: str):
+    if not Path(input_file).exists():
+        raise FileNotFoundError(f"{input_file} is not found")
+
+
+def _validate_fastq_extension(fastq_path: str):
     if not re.search(r".fastq$|.fastq.gz$|.fq$|.fq.gz$", fastq_path):
-        raise AttributeError(f"{fastq_path} requires extensions either 'fastq', 'fastq.gz', 'fq' or 'fq.gz'")
-
-
-# Varidate if the file is in the proper format. See top 100 lines
-def _fastq_content(fastq_path: str):
-    name, seq, qual = [], [], []
-    for i, (n, s, q) in enumerate(mappy.fastx_read(fastq_path)):
-        name.append(n)
-        seq.append(s)
-        qual.append(q)
-        if i == 100:
-            break
-    if not (len(name) == len(seq) == len(qual) > 0):
-        raise AttributeError(f"{fastq_path} is not a FASTQ format")
-
-
-def _fasta_content(fasta_path: str):
-    name, seq = [], []
-    for n, s, _ in mappy.fastx_read(fasta_path):
-        name.append(n)
-        seq.append(s)
-    if not len(name) == len(seq) > 0:
-        raise AttributeError(f"{fasta_path} is not a FASTA format")
-    if len(name) > len(set(name)):
-        raise AttributeError(f"{fasta_path} must include unique identifiers")
-    if len(seq) > len(set(seq)):
-        raise AttributeError(f"{fasta_path} must include unique DNA sequences")
-    if name.count("control") == 0:
-        raise AttributeError(f"One of the headers in the {fasta_path} must be '>control'")
+        raise ValueError(f"{fastq_path} requires extensions either 'fastq', 'fastq.gz', 'fq' or 'fq.gz'")
+
+
+# Varidate if the file is in the proper format.
+# See top 100 lines
+def _validate_fastq_content(fastq_path: str):
+    try:
+        names, seqs, quals = zip(*[(n, s, q) for i, (n, s, q) in enumerate(mappy.fastx_read(fastq_path)) if i < 100])
+        if not (len(names) == len(seqs) == len(quals) > 0):
+            raise ValueError
+    except ValueError:
+        raise ValueError(f"{fastq_path} is not a FASTQ format")
+
+
+def _validate_fasta_content(fasta_path: str):
+    try:
+        names, seqs = zip(*[(n, s) for n, s, _ in mappy.fastx_read(fasta_path)])
+        if len(names) != len(seqs) or not names:
+            raise ValueError
+    except ValueError:
+        raise ValueError(f"{fasta_path} is not a proper FASTA format")
+    if len(names) != len(set(names)):
+        raise ValueError(f"{fasta_path} must include unique identifiers")
+    if len(seqs) != len(set(seqs)):
+        raise ValueError(f"{fasta_path} must include unique DNA sequences")
+    if "control" not in names:
+        raise ValueError(f"One of the headers in the {fasta_path} must be '>control'")
 
 
 def validate_files(SAMPLE: str, CONTROL: str, ALLELE: str) -> None:
-    _exist_file(CONTROL)
-    _exist_file(SAMPLE)
-    _exist_file(ALLELE)
-    _fastq_extension(CONTROL)
-    _fastq_content(CONTROL)
-    _fastq_extension(SAMPLE)
-    _fastq_content(SAMPLE)
-    _fasta_content(ALLELE)
+    for file in [CONTROL, SAMPLE, ALLELE]:
+        _validate_file_existence(file)
+    for file in [CONTROL, SAMPLE]:
+        _validate_fastq_extension(file)
+        _validate_fastq_content(file)
+    _validate_fasta_content(ALLELE)
 
 
 ########################################################################
@@ -92,58 +89,72 @@ def exists_cached_genome(genome: str, tempdir: Path, exists_cache_control: bool)
 ########################################################################
 
 
-def _check_url_availability(url: str) -> bool:
+def _is_webpage_available(url: str) -> bool:
     try:
-        _ = urlopen(url, timeout=10)
-        return True
-    except (URLError, TimeoutError):
+        with urlopen(url) as response:
+            return 200 <= response.status < 300
+    except URLError:
         return False
 
 
 def get_first_available_url(urls: list[str]) -> str | None:
-    return next((url for url in urls if _check_url_availability(url)), None)
+    return next((url for url in urls if _is_webpage_available(url)), None)
 
 
-def is_genome_listed_in_UCSC(genome: str, ucsc_url: str) -> bool:
-    url = f"{ucsc_url}/cgi-bin/das/{genome}/dna?segment=1:1,10"
-    try:
-        response = urlopen(url, timeout=10)
-        return bool(response.read())
-    except (URLError, TimeoutError):
-        return False
+def _fetch_xml_data(url: str) -> bytes:
+    """Fetch XML data from a given URL."""
+    with urlopen(url) as response:
+        return response.read()
+
+
+def _extract_genome_ids_from_xml(xml_data: bytes) -> set:
+    """Extract genome IDs from XML data."""
+    root = ET.fromstring(xml_data)
+    return {cc.attrib["id"] for child in root for cc in child if cc.tag == "SOURCE"}
+
+
+def _get_genome_ids_in_ucsc(url_das: str) -> set:
+    """Get available genome IDs in UCSC."""
+    xml_data = _fetch_xml_data(url_das)
+    return _extract_genome_ids_from_xml(xml_data)
+
+
+def is_genome_in_ucsc_ids(genome: str, url_das: str) -> bool:
+    genome_ids = _get_genome_ids_in_ucsc(url_das)
+    return genome in genome_ids
 
 
 def validate_genome_and_fetch_urls(genome: str) -> dict[str, str]:
-    ucsc_blat_servers = [
-        "https://genome.ucsc.edu/cgi-bin/hgBlat",
-        "https://genome-asia.ucsc.edu/cgi-bin/hgBlat",
-        "https://genome-euro.ucsc.edu/cgi-bin/hgBlat",
-    ]
-    ucsc_das_servers = [
-        "https://genome.ucsc.edu/cgi-bin/das/dsn/",
-        "https://genome-asia.ucsc.edu/cgi-bin/das/dsn/",
-        "https://genome-euro.ucsc.edu/cgi-bin/das/dsn",
-    ]
-    goldenpath_servers = [
-        "https://hgdownload.cse.ucsc.edu/goldenPath",
-        "http://hgdownload-euro.soe.ucsc.edu/goldenPath",
-    ]
-    available_servers = {
-        "blat": get_first_available_url(ucsc_blat_servers),
-        "das": get_first_available_url(ucsc_das_servers),
-        "goldenpath": get_first_available_url(goldenpath_servers),
+    server_lists = {
+        "blat": [
+            "https://genome.ucsc.edu/cgi-bin/hgBlat",
+            "https://genome-asia.ucsc.edu/cgi-bin/hgBlat",
+            "https://genome-euro.ucsc.edu/cgi-bin/hgBlat",
+        ],
+        "das": [
+            "https://genome.ucsc.edu/cgi-bin/das/dsn/",
+            "https://genome-asia.ucsc.edu/cgi-bin/das/dsn/",
+            "https://genome-euro.ucsc.edu/cgi-bin/das/dsn",
+        ],
+        "goldenpath": [
+            "https://hgdownload.cse.ucsc.edu/goldenPath",
+            "http://hgdownload-euro.soe.ucsc.edu/goldenPath",
+        ],
     }
 
-    if not available_servers["blat"]:
-        raise URLError("All UCSC blat servers are currently down. Please wait for a while and try again.")
+    available_servers = {key: get_first_available_url(urls) for key, urls in server_lists.items()}
 
-    if not available_servers["goldenpath"]:
-        raise URLError("All UCSC GoldenPath servers are currently down. Please wait for a while and try again.")
+    error_messages = {
+        "blat": "All UCSC blat servers are currently down. Please wait for a while and try again.",
+        "das": "All UCSC DAS servers are currently down. Please wait for a while and try again.",
+        "goldenpath": "All UCSC GoldenPath servers are currently down. Please wait for a while and try again.",
+    }
 
-    if not available_servers["das"]:
-        raise URLError("All UCSC DAS servers are currently down. Please wait for a while and try again.")
+    for key, message in error_messages.items():
+        if not available_servers[key]:
+            raise URLError(message)
 
-    if not is_genome_listed_in_UCSC(genome, available_servers["das"]):
-        raise AttributeError(f"{genome} is not listed. Available genomes are in {available_servers['das']}")
+    if not is_genome_in_ucsc_ids(genome, available_servers["das"]):
+        raise ValueError(f"{genome} is not listed. Available genomes are in {available_servers['das']}")
 
     return available_servers
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 00000000..b32fbd0e
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,14 @@
+import pytest
+
+
+def pytest_addoption(parser):
+    parser.addoption("--runslow", action="store_true", default=False, help="run slow tests")
+
+
+def pytest_configure(config):
+    config.addinivalue_line("markers", "slow: mark test as slow to run")
+
+
+def pytest_runtest_setup(item):
+    if "slow" in item.keywords and not item.config.getoption("--runslow"):
+        pytest.skip("need --runslow option to run")
diff --git a/tests/src/preprocess/test_validate_inputs.py b/tests/src/preprocess/test_validate_inputs.py
index daf51e3e..1407cd8c 100644
--- a/tests/src/preprocess/test_validate_inputs.py
+++ b/tests/src/preprocess/test_validate_inputs.py
@@ -1,8 +1,5 @@
 import pytest
 from DAJIN2.preprocess import validate_inputs
-from importlib import reload
-
-reload(validate_inputs)
 
 
 ###############################################################################
@@ -13,7 +10,7 @@
 def test_exists():
     with pytest.raises(FileNotFoundError) as e:
         test = "filenotfound.txt"
-        validate_inputs._exist_file(test)
+        validate_inputs._validate_file_existence(test)
     assert str(e.value) == f"{test} is not found"
 
 
@@ -23,21 +20,21 @@ def test_exists():
 
 
 def test_fastq_extension():
-    with pytest.raises(AttributeError) as e:
+    with pytest.raises(ValueError) as e:
         test = "test.fqq"
-        validate_inputs._fastq_extension("test.fqq")
+        validate_inputs._validate_fastq_extension("test.fqq")
     assert str(e.value) == f"{test} requires extensions either 'fastq', 'fastq.gz', 'fq' or 'fq.gz'"
 
 
 def test_fastq_error_not_fastq_format():
-    with pytest.raises(AttributeError):
+    with pytest.raises(ValueError):
         fastq_path = "tests/data/preprocess/validate_inputs/empty.fq"
-        _ = validate_inputs._fastq_content(fastq_path)
+        _ = validate_inputs._validate_fastq_content(fastq_path)
 
 
 def test_fastq_without_error():
     fasta_path = "tests/data/preprocess/validate_inputs/control.fq.gz"
-    assert validate_inputs._fastq_content(fasta_path) is None
+    assert validate_inputs._validate_fastq_content(fasta_path) is None
 
 
 ###############################################################################
@@ -45,37 +42,37 @@ def test_fastq_without_error():
 ###############################################################################
 
 
-def test_fasta_error_not_fasta_format():
-    with pytest.raises(AttributeError) as e:
+def test_non_proper_fasta_format():
+    with pytest.raises(ValueError) as e:
         fasta_path = "tests/data/preprocess/validate_inputs/empty.fa"
-        _ = validate_inputs._fasta_content(fasta_path)
-    assert str(e.value) == f"{fasta_path} is not a FASTA format"
+        _ = validate_inputs._validate_fasta_content(fasta_path)
+    assert str(e.value) == f"{fasta_path} is not a proper FASTA format"
 
 
 def test_fasta_error_duplicated_identifiers():
-    with pytest.raises(AttributeError) as e:
+    with pytest.raises(ValueError) as e:
         fasta_path = "tests/data/preprocess/validate_inputs/duplicated_name.fa"
-        _ = validate_inputs._fasta_content(fasta_path)
+        _ = validate_inputs._validate_fasta_content(fasta_path)
     assert str(e.value) == f"{fasta_path} must include unique identifiers"
 
 
 def test_fasta_error_duplicated_sequences():
-    with pytest.raises(AttributeError) as e:
+    with pytest.raises(ValueError) as e:
         fasta_path = "tests/data/preprocess/validate_inputs/duplicated_seq.fa"
-        _ = validate_inputs._fasta_content(fasta_path)
+        _ = validate_inputs._validate_fasta_content(fasta_path)
     assert str(e.value) == f"{fasta_path} must include unique DNA sequences"
 
 
 def test_fasta_error_without_control():
-    with pytest.raises(AttributeError) as e:
+    with pytest.raises(ValueError) as e:
         fasta_path = "tests/data/preprocess/validate_inputs/no_control.fa"
-        _ = validate_inputs._fasta_content(fasta_path)
+        _ = validate_inputs._validate_fasta_content(fasta_path)
     assert str(e.value) == f"One of the headers in the {fasta_path} must be '>control'"
 
 
 def test_fasta_without_error():
     fasta_path = "tests/data/preprocess/validate_inputs/design_stx2.fa"
-    assert validate_inputs._fasta_content(fasta_path) is None
+    assert validate_inputs._validate_fasta_content(fasta_path) is None
 
 
 ###############################################################################
@@ -83,32 +80,39 @@ def test_fasta_without_error():
 ###############################################################################
 
 
-@pytest.mark.skip("This test takes long time due to URL access")
+@pytest.mark.slow
 def test_available_url_pass():
-    flag = validate_inputs._check_url_availabilities(["https://example.com"])
-    assert flag == [True]
+    assert validate_inputs._is_webpage_available("https://example.com") is True
 
 
-@pytest.mark.skip("This test takes long time due to URL access")
+@pytest.mark.slow
 def test_available_url_fail():
-    flag = validate_inputs._check_url_availabilities(["https://example_xxx.com"])
-    assert flag == [False]
+    assert validate_inputs._is_webpage_available("https://example_xxx.com") is False
+
+
+@pytest.mark.slow
+def test_get_first_available_url():
+    test = validate_inputs.get_first_available_url(["https://example_xxx.com", "https://example.com"])
+    answer = "https://example.com"
+    assert test == answer
+
+
+@pytest.mark.slow
+def test_get_first_available_url_not_found():
+    test = validate_inputs.get_first_available_url(["https://example_xxx.com", "https://example_yyy.com"])
+    answer = None
+    assert test == answer
 
 
-@pytest.mark.skip("This test takes long time due to URL access")
+@pytest.mark.slow
 def test_available_genome_pass():
     genome = "mm10"
-    ucsc_url = "https://genome.ucsc.edu/"
-    assert validate_inputs._is_listed(genome, ucsc_url) is None
+    url_das = "https://genome.ucsc.edu/cgi-bin/das/dsn"
+    assert validate_inputs.is_genome_in_ucsc_ids(genome, url_das) is True
 
 
-@pytest.mark.skip("This test takes long time due to URL access")
+@pytest.mark.slow
 def test_available_genome_fail():
-    genome = "xxxx"
-    ucsc_url = "https://genome.ucsc.edu/"
-    with pytest.raises(AttributeError) as e:
-        validate_inputs._is_listed(genome, ucsc_url)
-    assert (
-        str(e.value)
-        == f"{genome} is not listed in UCSC genome browser. Available genomes are in {ucsc_url}/cgi-bin/das/dsn"
-    )
+    genome = "mm12345"
+    url_das = "https://genome.ucsc.edu/cgi-bin/das/dsn"
+    assert validate_inputs.is_genome_in_ucsc_ids(genome, url_das) is False