diff --git a/main.py b/main.py
index e3c7ddd..25baa74 100644
--- a/main.py
+++ b/main.py
@@ -1,5 +1,19 @@
 from Bio import SeqIO
 from Bio.SeqUtils import gc_fraction
+from parser import parser
+import sys
+import logging
+
+logging.basicConfig(
+    filename="logs.log",
+    filemode="w",
+    format="{asctime} {levelname} +++ {message}",
+    datefmt="%Y-%m-%d %H:%M:%S",
+    style="{",
+    level=logging.INFO,
+    force=True,
+    encoding="utf-8",
+)
 
 
 class BiologicalSequence:
@@ -150,13 +164,70 @@ def filter_fastq(
 ) -> None:
     if isinstance(gc_bounds, float | int):
         gc_bounds = [gc_bounds, 100]
+    elif isinstance(gc_bounds, tuple):
+        gc_bounds = [gc_bounds[0], gc_bounds[1]]
 
     if isinstance(length_bounds, float | int):
         length_bounds = [length_bounds, 2 ** 32]
+    elif isinstance(length_bounds, tuple):
+        length_bounds = [length_bounds[0], length_bounds[1]]
 
     with open(input_fastq, "r") as input_fastq, open(output_fastq, "w") as output_fastq:
         for record in SeqIO.parse(input_fastq, "fastq"):
             if min(record.letter_annotations["phred_quality"]) >= quality_threshold:
-                if gc_bounds[0] < gc_fraction(record.seq) * 100 < gc_bounds[1]:
-                    if length_bounds[0] < len(record.seq) < length_bounds[1]:
+                if gc_bounds[0] <= gc_fraction(record.seq) * 100 <= gc_bounds[1]:
+                    if length_bounds[0] <= len(record.seq) <= length_bounds[1]:
                         SeqIO.write(record, output_fastq, "fastq")
+
+
+if __name__ == "__main__":
+    if len(sys.argv) == 1:
+        parser.print_help(sys.stderr)
+        sys.exit(1)
+
+    args = parser.parse_args()
+    input_fastq = args.input_fastq
+    output_fastq = args.output_fastq
+    # parse gc_bounds
+    if args.gc_bounds is None:
+        gc_bounds = (0, 100)
+    else:
+        if len(args.gc_bounds) == 1:
+            gc_bounds = int(args.gc_bounds[0])
+        elif len(args.gc_bounds) == 2:
+            gc_bounds = tuple(filter(lambda x: float(x), args.gc_bounds))
+            if gc_bounds[0] > gc_bounds[1]:
+                gc_bounds = (gc_bounds[1], gc_bounds[0])
+                logging.error(
+                    f"Mistake the order of gc-bounds. New order is {gc_bounds}"
+                )
+        else:
+            raise Exception
+
+    # parse length_bounds
+    if args.length_bounds is None:
+        length_bounds = (0, 2 ** 32)
+    else:
+        if len(args.length_bounds) == 1:
+            length_bounds = int(args.length_bounds[0])
+        elif len(args.length_bounds) == 2:
+            length_bounds = tuple(filter(lambda x: int(x), args.length_bounds))
+        else:
+            raise Exception
+    # parse quality_threshold
+    if args.quality_threshold is None:
+        quality_threshold = 0
+    else:
+        quality_threshold = int(args.quality_threshold[0])
+
+    filter_fastq(input_fastq, output_fastq, gc_bounds, length_bounds, quality_threshold)
+
+    logging.info(
+        f"Fastq filtration with options:\n"
+        f"  - input file: {input_fastq}\n"
+        f"  - output file: {output_fastq}\n"
+        f"  - gc_bounds: {gc_bounds}\n"
+        f"  - length_bounds: {length_bounds}\n"
+        f"  - quality_threshold: {quality_threshold}\n"
+        "Performed successfully."
+    )
diff --git a/parser.py b/parser.py
new file mode 100644
index 0000000..23f1142
--- /dev/null
+++ b/parser.py
@@ -0,0 +1,35 @@
+import argparse
+
+parser = argparse.ArgumentParser(
+    prog="FASTQ FILTRATOR",
+    description="This tool filtrate nucleotide reads from fastq file by gc_content, length and quality treshold.",
+    epilog="Enjoy FASTQ FILTRATOR tool!",
+)
+
+parser.add_argument("input_fastq", type=str, help="Takes path to input fastq file")
+parser.add_argument(
+    "output_fastq", type=str, help="Takes path to output filtrated fastq file"
+)
+parser.add_argument(
+    "-gc",
+    "--gc_bounds",
+    metavar="%%",
+    type=float,
+    nargs="+",
+    help="Takes one or two floats as the limitation of gc content (in %%). Default from 0 to 100 percentages.",
+)
+parser.add_argument(
+    "-lb",
+    "--length_bounds",
+    metavar="bp",
+    type=int,
+    nargs="+",
+    help="Takes one or two intagers as the limitation of length of reads. Default from 0 to 2 ** 32 bp.",
+)
+parser.add_argument(
+    "-qt",
+    "--quality_threshold",
+    type=int,
+    nargs=1,
+    help="Takes one intager as the limitation of read quality. Default is 0.",
+)
diff --git a/requirments.txt b/requirments.txt
index 0428672..3ea7050 100644
--- a/requirments.txt
+++ b/requirments.txt
@@ -1,2 +1,3 @@
 biopython==1.85
 numpy==2.2.3
+pytest==8.3.3
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_fastq_filtrator.py b/tests/test_fastq_filtrator.py
new file mode 100644
index 0000000..39c9ce9
--- /dev/null
+++ b/tests/test_fastq_filtrator.py
@@ -0,0 +1,138 @@
+import os.path
+
+import pytest
+
+from main import filter_fastq
+
+
+def get_output_data(output):
+    result = []
+    with open(output) as file:
+        for line in file:
+            result.append(line.strip("\n"))
+    return result
+
+
+@pytest.fixture
+def tmp_input():
+    file_path = "tmp_input.fastq"
+    with open(file_path, "w") as fastq:
+        fastq.write("@one\nAAAAA\n+\n@@@@@\n")
+        fastq.write("@two\nATGC\n+\n@@@@\n")
+        fastq.write("@three\nGGG\n+\nEEE\n")
+
+    yield file_path
+
+    if os.path.exists(file_path):
+        os.remove(file_path)
+
+
+@pytest.fixture
+def tmp_incorrect_fastq_input():
+    file_path = "tmp_input_incorrect.fastq"
+    with open(file_path, "w") as fastq:
+        fastq.write("@incorr\n\n+\n\n")  # нет последоват-ти
+        fastq.write("@corr\nGGG\n+\nFFF\n")
+
+    yield file_path
+
+    if os.path.exists(file_path):
+        os.remove(file_path)
+
+
+@pytest.fixture
+def tmp_output():
+    file_path = "tmp_output.fastq"
+
+    yield file_path
+
+    if os.path.exists(file_path):
+        os.remove(file_path)
+
+
+def test_filter_fastq_input_file_not_exists(tmp_output):
+    with pytest.raises(FileNotFoundError):
+        filter_fastq(input_fastq="....", output_fastq=tmp_output)
+
+
+def test_filter_fastq_file_incorrect(tmp_incorrect_fastq_input, tmp_output):
+    with pytest.raises(ValueError):
+        filter_fastq(input_fastq=tmp_incorrect_fastq_input, output_fastq=tmp_output)
+
+
+def test_filter_fastq_output_exists(tmp_input, tmp_output):
+    filter_fastq(input_fastq=tmp_input, output_fastq=tmp_output)
+    assert os.path.exists(tmp_output)
+
+
+def test_filter_fastq_with_default(tmp_input, tmp_output):
+    filter_fastq(input_fastq=tmp_input, output_fastq=tmp_output)
+
+    expected_result = [
+        "@one",
+        "AAAAA",
+        "+",
+        "@@@@@",
+        "@two",
+        "ATGC",
+        "+",
+        "@@@@",
+        "@three",
+        "GGG",
+        "+",
+        "EEE",
+    ]
+
+    assert get_output_data(tmp_output) == expected_result
+
+
+def test_filter_fastq_by_len(tmp_input, tmp_output):
+    filter_fastq(input_fastq=tmp_input, output_fastq=tmp_output, length_bounds=5)
+
+    expected_result = [
+        "@one",
+        "AAAAA",
+        "+",
+        "@@@@@",
+    ]
+
+    assert get_output_data(tmp_output) == expected_result
+
+
+def test_filter_fastq_by_gc(tmp_input, tmp_output):
+    filter_fastq(input_fastq=tmp_input, output_fastq=tmp_output, gc_bounds=(90, 100))
+
+    expected_result = [
+        "@three",
+        "GGG",
+        "+",
+        "EEE",
+    ]
+
+    assert get_output_data(tmp_output) == expected_result
+
+
+def test_filter_fastq_by_gc_only_lower_bound(tmp_input, tmp_output):
+    filter_fastq(input_fastq=tmp_input, output_fastq=tmp_output, gc_bounds=90)
+
+    expected_result = [
+        "@three",
+        "GGG",
+        "+",
+        "EEE",
+    ]
+
+    assert get_output_data(tmp_output) == expected_result
+
+
+def test_filter_fastq_by_quality(tmp_input, tmp_output):
+    filter_fastq(input_fastq=tmp_input, output_fastq=tmp_output, quality_threshold=32)
+
+    expected_result = [
+        "@three",
+        "GGG",
+        "+",
+        "EEE",
+    ]
+
+    assert get_output_data(tmp_output) == expected_result