diff --git a/core/tests/test_trezor.ui.text.py b/core/tests/test_trezor.ui.text.py
new file mode 100644
index 000000000..086cf0bb5
--- /dev/null
+++ b/core/tests/test_trezor.ui.text.py
@@ -0,0 +1,149 @@
+import mock
+from common import *
+
+from trezor import ui
+from trezor.ui import text, display
+
+if False:
+    from typing import List, Tuple
+
+
+class TestTextSpan(unittest.TestCase):
+    def lines(self, span: text.Span) -> List[Tuple[str, int, bool]]:
+        result = []
+        while True:
+            should_continue = span.next_line()
+            substr = span.string[span.start : span.start + span.length]
+            result.append((substr, span.width, span.word_break))
+            if not should_continue:
+                break
+        return result
+
+    def checkSpanWithoutWidths(
+        self, span: text.Span, expected: List[Tuple[str, bool]]
+    ) -> None:
+        expected_with_calculated_widths = [
+            (string, ui.display.text_width(string, span.font), word_break)
+            for string, word_break in expected
+        ]
+        self.assertListEqual(self.lines(span), expected_with_calculated_widths)
+
+    def test_basic(self):
+        span = text.Span("hello")
+        self.checkSpanWithoutWidths(
+            span,
+            [("hello", False)],
+        )
+
+        span.reset("world", start=0, font=ui.NORMAL)
+        self.checkSpanWithoutWidths(
+            span,
+            [("world", False)],
+        )
+
+        span.reset("", start=0, font=ui.NORMAL)
+        self.checkSpanWithoutWidths(
+            span,
+            [("", False)],
+        )
+
+    def test_two_lines(self):
+        line_width = display.text_width("hello world", ui.NORMAL) - 1
+        span = text.Span("hello world", line_width=line_width)
+        self.checkSpanWithoutWidths(
+            span,
+            [
+                ("hello", False),
+                ("world", False),
+            ],
+        )
+
+    def test_newlines(self):
+        span = text.Span("hello\nworld")
+        self.checkSpanWithoutWidths(
+            span,
+            [
+                ("hello", False),
+                ("world", False),
+            ],
+        )
+
+        span = text.Span("\nhello\nworld\n")
+        self.checkSpanWithoutWidths(
+            span,
+            [
+                ("", False),
+                ("hello", False),
+                ("world", False),
+                ("", False),
+            ],
+        )
+
+    def test_break_words(self):
+        line_width = display.text_width("hello w", ui.NORMAL) + text.DASH_WIDTH
+        span = text.Span("hello world", line_width=line_width, break_words=True)
+        self.checkSpanWithoutWidths(
+            span,
+            [
+                ("hello w", True),
+                ("orld", False),
+            ],
+        )
+
+    def test_long_word(self):
+        line_width = display.text_width("establishme", ui.NORMAL) + text.DASH_WIDTH
+        span = text.Span(
+            "Down with the establishment!", line_width=line_width, break_words=False
+        )
+        self.checkSpanWithoutWidths(
+            span,
+            [
+                ("Down with", False),
+                ("the", False),
+                ("establishme", True),
+                ("nt!", False),
+            ],
+        )
+
+    def test_has_more_content(self):
+        line_width = display.text_width("hello world", ui.NORMAL) - 1
+        span = text.Span("hello world", line_width=line_width)
+        self.assertTrue(span.has_more_content())
+        self.assertTrue(span.next_line())
+        self.assertEqual("hello", span.string[span.start : span.start + span.length])
+
+        # has_more_content is True because there's text remaining on the line
+        self.assertTrue(span.has_more_content())
+        # next_line is False because we should not continue iterating
+        self.assertFalse(span.next_line())
+        self.assertEqual("world", span.string[span.start : span.start + span.length])
+
+        self.assertFalse(span.has_more_content())
+        self.assertFalse(span.next_line())
+        self.assertEqual("world", span.string[span.start : span.start + span.length])
+
+
+    def test_has_more_content_trailing_newline(self):
+        span = text.Span("1\n2\n3\n")
+
+        self.assertTrue(span.has_more_content())
+        self.assertTrue(span.next_line())
+        self.assertEqual("1", span.string[span.start : span.start + span.length])
+
+        self.assertTrue(span.has_more_content())
+        self.assertTrue(span.next_line())
+        self.assertEqual("2", span.string[span.start : span.start + span.length])
+
+        self.assertTrue(span.has_more_content())
+        self.assertTrue(span.next_line())
+        self.assertEqual("3", span.string[span.start : span.start + span.length])
+
+        # has_more_content is False because the "remaining" text is empty
+        self.assertFalse(span.has_more_content())
+        # next_line is False because we should not continue iterating
+        self.assertFalse(span.next_line())
+        self.assertEqual("", span.string[span.start : span.start + span.length])
+
+
+if __name__ == "__main__":
+    unittest.main()