diff --git a/tests/unit/test_conversation_models.py b/tests/unit/test_conversation_models.py
new file mode 100644
index 0000000..59aa699
--- /dev/null
+++ b/tests/unit/test_conversation_models.py
@@ -0,0 +1,242 @@
+"""
+Unit Tests — Conversation Models
+=================================
+
+Tests for the new SQLAlchemy conversation models (mock-based, no DB required):
+- Conversation.display_name
+- Conversation.member_count
+- ConversationMember.is_owner
+- ConvMessage.__repr__
+- MessageReaction unique constraint
+- Model imports
+"""
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))))
+
+import pytest
+from unittest.mock import MagicMock
+from sqlalchemy import UniqueConstraint
+
+
+# ============================================================
+# Import Tests
+# ============================================================
+
+class TestModelImports:
+    """Verify all 5 conversation models can be imported from database."""
+
+    def test_import_conversation(self):
+        from database import Conversation
+        assert Conversation is not None
+
+    def test_import_conversation_member(self):
+        from database import ConversationMember
+        assert ConversationMember is not None
+
+    def test_import_conv_message(self):
+        from database import ConvMessage
+        assert ConvMessage is not None
+
+    def test_import_message_reaction(self):
+        from database import MessageReaction
+        assert MessageReaction is not None
+
+    def test_import_message_attachment(self):
+        from database import MessageAttachment
+        assert MessageAttachment is not None
+
+
+# ============================================================
+# Helpers
+# ============================================================
+
+def _make_mock_member(name=None, email='user@example.com'):
+    """Create a MagicMock simulating a ConversationMember with a User."""
+    member = MagicMock()
+    user = MagicMock()
+    user.name = name
+    user.email = email
+    member.user = user
+    return member
+
+
+def _make_conversation(name=None, members=None):
+    """Create a MagicMock simulating a Conversation instance."""
+    from database import Conversation
+    conv = MagicMock(spec=Conversation)
+    # Attach the real property logic by calling it on the mock
+    conv.name = name
+    conv.members = members or []
+    # Bind the real display_name property to this mock
+    conv.display_name = Conversation.display_name.fget(conv)
+    conv.member_count = Conversation.member_count.fget(conv)
+    return conv
+
+
+# ============================================================
+# Conversation.display_name Tests
+# ============================================================
+
+class TestConversationDisplayName:
+    """Test Conversation.display_name property."""
+
+    def test_display_name_returns_name_when_set(self):
+        from database import Conversation
+        conv = MagicMock()
+        conv.name = 'Projekt Alpha'
+        conv.members = []
+        result = Conversation.display_name.fget(conv)
+        assert result == 'Projekt Alpha'
+
+    def test_display_name_joins_member_names_when_no_name(self):
+        from database import Conversation
+        conv = MagicMock()
+        conv.name = None
+        conv.members = [
+            _make_mock_member(name='Anna'),
+            _make_mock_member(name='Bob'),
+        ]
+        result = Conversation.display_name.fget(conv)
+        assert 'Anna' in result
+        assert 'Bob' in result
+
+    def test_display_name_uses_email_prefix_when_user_has_no_name(self):
+        from database import Conversation
+        conv = MagicMock()
+        conv.name = None
+        conv.members = [
+            _make_mock_member(name=None, email='jan.kowalski@example.com'),
+        ]
+        result = Conversation.display_name.fget(conv)
+        assert 'jan.kowalski' in result
+
+    def test_display_name_truncates_beyond_four_members(self):
+        from database import Conversation
+        conv = MagicMock()
+        conv.name = None
+        conv.members = [
+            _make_mock_member(name=f'User{i}', email=f'user{i}@example.com')
+            for i in range(6)
+        ]
+        result = Conversation.display_name.fget(conv)
+        assert '+2' in result
+
+    def test_display_name_no_suffix_for_four_or_fewer_members(self):
+        from database import Conversation
+        conv = MagicMock()
+        conv.name = None
+        conv.members = [
+            _make_mock_member(name=f'User{i}', email=f'user{i}@example.com')
+            for i in range(4)
+        ]
+        result = Conversation.display_name.fget(conv)
+        assert '+' not in result
+
+
+# ============================================================
+# Conversation.member_count Tests
+# ============================================================
+
+class TestConversationMemberCount:
+    """Test Conversation.member_count property."""
+
+    def test_member_count_returns_length_of_members(self):
+        from database import Conversation
+        conv = MagicMock()
+        conv.members = [MagicMock(), MagicMock(), MagicMock()]
+        assert Conversation.member_count.fget(conv) == 3
+
+    def test_member_count_zero_when_no_members(self):
+        from database import Conversation
+        conv = MagicMock()
+        conv.members = []
+        assert Conversation.member_count.fget(conv) == 0
+
+
+# ============================================================
+# ConversationMember.is_owner Tests
+# ============================================================
+
+class TestConversationMemberIsOwner:
+    """Test ConversationMember.is_owner property."""
+
+    def test_is_owner_true_when_role_is_owner(self):
+        from database import ConversationMember
+        cm = MagicMock()
+        cm.role = 'owner'
+        assert ConversationMember.is_owner.fget(cm) is True
+
+    def test_is_owner_false_when_role_is_member(self):
+        from database import ConversationMember
+        cm = MagicMock()
+        cm.role = 'member'
+        assert ConversationMember.is_owner.fget(cm) is False
+
+    def test_is_owner_false_when_role_is_admin(self):
+        from database import ConversationMember
+        cm = MagicMock()
+        cm.role = 'admin'
+        assert ConversationMember.is_owner.fget(cm) is False
+
+    def test_is_owner_false_when_role_is_empty(self):
+        from database import ConversationMember
+        cm = MagicMock()
+        cm.role = ''
+        assert ConversationMember.is_owner.fget(cm) is False
+
+
+# ============================================================
+# ConvMessage.__repr__ Tests
+# ============================================================
+
+class TestConvMessageRepr:
+    """Test ConvMessage.__repr__ returns expected format."""
+
+    def test_repr_format(self):
+        from database import ConvMessage
+        msg = MagicMock()
+        msg.id = 42
+        msg.conversation_id = 7
+        msg.sender_id = 13
+        # Call the actual __repr__ method on the mock instance
+        result = ConvMessage.__repr__(msg)
+        assert '42' in result
+        assert '7' in result
+        assert '13' in result
+
+    def test_repr_contains_class_indicator(self):
+        from database import ConvMessage
+        msg = MagicMock()
+        msg.id = 1
+        msg.conversation_id = 2
+        msg.sender_id = 3
+        assert 'ConvMessage' in ConvMessage.__repr__(msg)
+
+
+# ============================================================
+# MessageReaction UniqueConstraint Tests
+# ============================================================
+
+class TestMessageReactionUniqueConstraint:
+    """Verify MessageReaction __table_args__ contains UniqueConstraint."""
+
+    def test_table_args_contains_unique_constraint(self):
+        from database import MessageReaction
+        table_args = MessageReaction.__table_args__
+        assert table_args is not None
+        constraint_types = [type(a) for a in table_args]
+        assert UniqueConstraint in constraint_types
+
+    def test_unique_constraint_covers_message_user_emoji(self):
+        from database import MessageReaction
+        table_args = MessageReaction.__table_args__
+        unique_constraints = [a for a in table_args if isinstance(a, UniqueConstraint)]
+        assert len(unique_constraints) >= 1
+        constraint = unique_constraints[0]
+        col_names = [col.key for col in constraint.columns]
+        assert 'message_id' in col_names
+        assert 'user_id' in col_names
+        assert 'emoji' in col_names
diff --git a/tests/unit/test_link_preview.py b/tests/unit/test_link_preview.py
new file mode 100644
index 0000000..9242425
--- /dev/null
+++ b/tests/unit/test_link_preview.py
@@ -0,0 +1,262 @@
+"""
+Unit Tests — Link Preview
+==========================
+
+Tests for blueprints/messages/link_preview.py:
+- OGParser with og: meta tags
+- OGParser fallback to <title> and meta description
+- OGParser with no meta tags
+- fetch_link_preview with no URL
+- fetch_link_preview skips internal URLs
+- fetch_link_preview success (mocked HTTP)
+- fetch_link_preview timeout handling
+- fetch_link_preview non-HTML content-type
+- URL extraction from HTML anchor tags
+"""
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))))
+
+import pytest
+from unittest.mock import patch, MagicMock
+from requests.exceptions import Timeout
+
+from blueprints.messages.link_preview import fetch_link_preview, OGParser
+
+
+# ============================================================
+# OGParser Tests
+# ============================================================
+
+class TestOGParser:
+    """Test OGParser HTML parsing."""
+
+    def test_parses_og_title_description_image(self):
+        html = """
+        <html><head>
+        <meta property="og:title" content="Test Title">
+        <meta property="og:description" content="Test Description">
+        <meta property="og:image" content="https://example.com/image.jpg">
+        </head></html>
+        """
+        parser = OGParser()
+        parser.feed(html)
+        assert parser.og['title'] == 'Test Title'
+        assert parser.og['description'] == 'Test Description'
+        assert parser.og['image'] == 'https://example.com/image.jpg'
+
+    def test_fallback_to_title_tag_and_meta_description(self):
+        html = """
+        <html><head>
+        <title>Fallback Title</title>
+        <meta name="description" content="Fallback Description">
+        </head></html>
+        """
+        parser = OGParser()
+        parser.feed(html)
+        assert parser.title == 'Fallback Title'
+        assert parser.og.get('description') == 'Fallback Description'
+        assert 'title' not in parser.og  # og:title not set
+
+    def test_empty_html_returns_title_from_title_tag(self):
+        html = "<html><head><title>Only Title</title></head></html>"
+        parser = OGParser()
+        parser.feed(html)
+        assert parser.title == 'Only Title'
+        assert parser.og.get('description') is None
+        assert parser.og.get('image') is None
+
+    def test_no_meta_tags_empty_og(self):
+        html = "<html><head></head><body>No meta here</body></html>"
+        parser = OGParser()
+        parser.feed(html)
+        assert parser.og == {}
+        assert parser.title is None
+
+    def test_og_description_takes_precedence_over_meta_description(self):
+        html = """
+        <html><head>
+        <meta property="og:description" content="OG Desc">
+        <meta name="description" content="Meta Desc">
+        </head></html>
+        """
+        parser = OGParser()
+        parser.feed(html)
+        assert parser.og['description'] == 'OG Desc'
+
+
+# ============================================================
+# fetch_link_preview Tests
+# ============================================================
+
+class TestFetchLinkPreview:
+    """Test fetch_link_preview function."""
+
+    def test_returns_none_for_none_text(self):
+        result = fetch_link_preview(None)
+        assert result is None
+
+    def test_returns_none_for_empty_text(self):
+        result = fetch_link_preview('')
+        assert result is None
+
+    def test_returns_none_when_no_url_in_text(self):
+        result = fetch_link_preview('Cześć, jak się masz?')
+        assert result is None
+
+    def test_returns_none_for_internal_nordabiznes_url(self):
+        result = fetch_link_preview('Sprawdź https://nordabiznes.pl/company/test')
+        assert result is None
+
+    def test_returns_none_for_staging_internal_url(self):
+        result = fetch_link_preview('Link: https://staging.nordabiznes.pl/company/foo')
+        assert result is None
+
+    def test_returns_none_for_localhost_url(self):
+        result = fetch_link_preview('Dev: http://localhost:5000/test')
+        assert result is None
+
+    def test_success_returns_dict_with_og_data(self):
+        html = """<html><head>
+        <meta property="og:title" content="Example Title">
+        <meta property="og:description" content="Example Description">
+        <meta property="og:image" content="https://example.com/img.jpg">
+        </head></html>"""
+
+        mock_resp = MagicMock()
+        mock_resp.headers = {'content-type': 'text/html; charset=utf-8'}
+        mock_resp.text = html
+        mock_resp.raise_for_status = MagicMock()
+
+        with patch('blueprints.messages.link_preview.requests.get', return_value=mock_resp):
+            result = fetch_link_preview('Check out https://example.com')
+
+        assert result is not None
+        assert result['url'] == 'https://example.com'
+        assert result['title'] == 'Example Title'
+        assert result['description'] == 'Example Description'
+        assert result['image'] == 'https://example.com/img.jpg'
+
+    def test_success_uses_title_tag_fallback(self):
+        html = "<html><head><title>Page Title</title></head></html>"
+
+        mock_resp = MagicMock()
+        mock_resp.headers = {'content-type': 'text/html'}
+        mock_resp.text = html
+        mock_resp.raise_for_status = MagicMock()
+
+        with patch('blueprints.messages.link_preview.requests.get', return_value=mock_resp):
+            result = fetch_link_preview('See https://example.com for details')
+
+        assert result is not None
+        assert result['title'] == 'Page Title'
+
+    def test_returns_none_on_timeout(self):
+        with patch('blueprints.messages.link_preview.requests.get', side_effect=Timeout):
+            result = fetch_link_preview('Visit https://slow-site.example.com')
+        assert result is None
+
+    def test_returns_none_for_non_html_content_type(self):
+        mock_resp = MagicMock()
+        mock_resp.headers = {'content-type': 'application/pdf'}
+        mock_resp.text = '%PDF-1.4 binary content'
+        mock_resp.raise_for_status = MagicMock()
+
+        with patch('blueprints.messages.link_preview.requests.get', return_value=mock_resp):
+            result = fetch_link_preview('Download https://example.com/doc.pdf')
+        assert result is None
+
+    def test_returns_none_when_page_has_no_title(self):
+        html = "<html><head><meta name='robots' content='noindex'></head></html>"
+
+        mock_resp = MagicMock()
+        mock_resp.headers = {'content-type': 'text/html'}
+        mock_resp.text = html
+        mock_resp.raise_for_status = MagicMock()
+
+        with patch('blueprints.messages.link_preview.requests.get', return_value=mock_resp):
+            result = fetch_link_preview('Visit https://example.com')
+        assert result is None
+
+    def test_title_truncated_to_200_chars(self):
+        long_title = 'A' * 300
+        html = f"<html><head><title>{long_title}</title></head></html>"
+
+        mock_resp = MagicMock()
+        mock_resp.headers = {'content-type': 'text/html'}
+        mock_resp.text = html
+        mock_resp.raise_for_status = MagicMock()
+
+        with patch('blueprints.messages.link_preview.requests.get', return_value=mock_resp):
+            result = fetch_link_preview('https://example.com')
+
+        assert result is not None
+        assert len(result['title']) <= 200
+
+    def test_description_truncated_to_300_chars(self):
+        long_desc = 'B' * 400
+        html = f"""<html><head>
+        <title>Title</title>
+        <meta name="description" content="{long_desc}">
+        </head></html>"""
+
+        mock_resp = MagicMock()
+        mock_resp.headers = {'content-type': 'text/html'}
+        mock_resp.text = html
+        mock_resp.raise_for_status = MagicMock()
+
+        with patch('blueprints.messages.link_preview.requests.get', return_value=mock_resp):
+            result = fetch_link_preview('https://example.com')
+
+        assert result is not None
+        assert len(result['description']) <= 300
+
+
+# ============================================================
+# URL Extraction from HTML Content Tests
+# ============================================================
+
+class TestURLExtractionFromHTML:
+    """Test that URLs inside HTML anchor tags are correctly found."""
+
+    def test_extracts_url_from_anchor_tag(self):
+        """URL inside <a href> is extracted after stripping HTML tags."""
+        text = '<a href="https://external-site.com/page">Visit site</a>'
+        # The function strips HTML tags before extracting URLs,
+        # so href URL is not extracted — only bare URLs in text are.
+        # This test verifies the stripping behavior: no URL in visible text → None.
+        result = fetch_link_preview(text)
+        # After stripping tags, text is "Visit site" — no URL → None
+        assert result is None
+
+    def test_extracts_bare_url_from_mixed_html(self):
+        """Bare URL in text alongside HTML is extracted correctly."""
+        text = '<p>Check out https://example.com/news for more</p>'
+
+        mock_resp = MagicMock()
+        mock_resp.headers = {'content-type': 'text/html'}
+        mock_resp.text = '<html><head><title>News</title></head></html>'
+        mock_resp.raise_for_status = MagicMock()
+
+        with patch('blueprints.messages.link_preview.requests.get', return_value=mock_resp):
+            result = fetch_link_preview(text)
+
+        assert result is not None
+        assert result['url'] == 'https://example.com/news'
+
+    def test_first_url_is_used_when_multiple_urls_present(self):
+        """When text contains multiple URLs, the first one is used."""
+        text = 'First: https://first.example.com and second: https://second.example.com'
+
+        mock_resp = MagicMock()
+        mock_resp.headers = {'content-type': 'text/html'}
+        mock_resp.text = '<html><head><title>First</title></head></html>'
+        mock_resp.raise_for_status = MagicMock()
+
+        with patch('blueprints.messages.link_preview.requests.get', return_value=mock_resp):
+            result = fetch_link_preview(text)
+
+        assert result is not None
+        assert result['url'] == 'https://first.example.com'