diff --git a/compiler/tests/test_lexer.py b/compiler/tests/test_lexer.py
index befeca4..aae42af 100644
--- a/compiler/tests/test_lexer.py
+++ b/compiler/tests/test_lexer.py
@@ -1,6 +1,9 @@
 import io
 
+import pytest
+
 from compiler.lexer import Tokens, TextIOWithMemory, Lexer, Token
+from compiler import errors
 
 
 def _check_token_type(lexer: Lexer, expected_tokens: list[Tokens]):
@@ -14,6 +17,11 @@ def _check_token_type(lexer: Lexer, expected_tokens: list[Tokens]):
     assert tuple(tokens) == tuple(expected_tokens)
 
 
+def test_lexer_misc():
+    # Tokens are supposed to be always true
+    assert Tokens.Blank
+
+
 def test_lexer_empty():
     data_raw = io.StringIO("")
     data = TextIOWithMemory(data_raw)
@@ -21,13 +29,14 @@ def test_lexer_empty():
     my_lexer = Lexer(input_stream=data)
     _check_token_type(my_lexer, [Tokens.BEGIN, Tokens.EOF])
 
+
 def test_lexer_arithmetic():
     data_raw = io.StringIO("1+5-41*2/1")
     data = TextIOWithMemory(data_raw)
 
     my_lexer = Lexer(input_stream=data)
     _check_token_type(my_lexer, [Tokens.BEGIN, Tokens.Integer, Tokens.Op_Plus, Tokens.Integer,
-                       Tokens.Op_Minus, Tokens.Integer, Tokens.Op_Multiply, Tokens.Integer,
+                                 Tokens.Op_Minus, Tokens.Integer, Tokens.Op_Multiply, Tokens.Integer,
                                  Tokens.Op_Divide, Tokens.Integer, Tokens.EOF])
 
 
@@ -47,3 +56,37 @@ def test_lexer_blocks():
         Tokens.Newline,
         Tokens.Blank, Tokens.Brace_Right, Tokens.Newline,
         Tokens.Blank, Tokens.EOF])
+
+
+def test_lexer_invalid_token():
+    with pytest.raises(errors.CompilationError) as e:
+        my_lexer = Lexer(input_stream=TextIOWithMemory(io.StringIO("4a")))
+
+        # Force lexer to consume all tokens
+        list(my_lexer)
+    assert e.type == errors.CompilationError
+    assert e.value.args == ("<none>:0:1: error: Unknown token 'a'\nLine 0: 4a\n         ^",)
+
+
+def test_lexer_eof():
+    my_lexer = Lexer(input_stream=TextIOWithMemory(io.StringIO("{ 1; }")))
+    # Force lexer to consume all tokens
+    list(my_lexer)
+
+    with pytest.raises(StopIteration) as e:
+        next(my_lexer)
+    assert e.type == StopIteration
+    assert e.value.args == ("EOF already reached",)
+
+    with pytest.raises(StopIteration) as e:
+        my_lexer._next_token()
+    assert e.type == StopIteration
+    assert e.value.args == ("EOF already reached",)
+
+
+def test_lexer_keyword_match():
+    # For entering the "Best match is a keyword and current match is not, skipping" branch
+    my_lexer = Lexer(input_stream=TextIOWithMemory(io.StringIO("{ let leta = 3; }")))
+
+    # Force lexer to consume all tokens
+    list(my_lexer)