diff --git a/.github/workflows/python-pytest.yml b/.github/workflows/python-pytest.yml
new file mode 100644
index 0000000..b82a09c
--- /dev/null
+++ b/.github/workflows/python-pytest.yml
@@ -0,0 +1,36 @@
+# This workflow will install Python dependencies, run tests and lint with a single version of Python
+# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python
+
+name: Execute tests with pytest
+
+on:
+  push:
+    branches: [ "dev" ]
+  pull_request:
+    branches: [ "dev", "main" ]
+permissions:
+  contents: read
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up Python 3.10
+      uses: actions/setup-python@v3
+      with:
+        python-version: "3.10"
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+        if [ -f tests/requirements.txt ]; then pip install -r tests/requirements.txt; fi
+    #    if [ -f pyproject.toml ]; then pip install -r pyproject.toml; fi
+    #- name: Lint with flake8
+    #  run: |
+    #    # stop the build if there are Python syntax errors or undefined names
+    #    flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
+    #    # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
+    #    flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+    - name: Test with pytest
+      run: |
+        pytest
diff --git a/docs/dev_notes.md b/docs/dev_notes.md
index 7c57bd1..5bf7a43 100644
--- a/docs/dev_notes.md
+++ b/docs/dev_notes.md
@@ -5,7 +5,7 @@ We set this up so it is hosted as a huggingface space. Each commit to `main` tri
 For local testing, assuming you have all the required packages installed in a
 conda env or virtualenv, and that env is activated:
 
-```
+```bash
 cd src
 streamlit run main.py
 ```
@@ -17,15 +17,17 @@ We have a CI action to presesnt the docs on github.io.
 To validate locally, you need the deps listed in `requirements.txt` installed. 
 
 Run
-```
+```bash
 mkdocs serve
 ```
+
 And navigate to the wish server running locally, by default: http://127.0.0.1:8888/
 
 This automatically watches for changes in the markdown files, but if you edit the 
 something else like the docstrings in py files, triggering a rebuild in another terminal
 refreshes the site, without having to quit and restart the server.
-```
+
+```bash
 mkdocs build -c
 ```
 
@@ -37,4 +39,44 @@ mkdocs build -c
 
 # Set up a conda env
 
-(Standard stuff)
\ No newline at end of file
+(Standard stuff)
+
+
+# Testing
+
+## local testing
+To run the tests locally, we have the standard dependencies of the project, plus the test runner dependencies. 
+
+```bash
+pip install -r tests/requirements.txt
+```
+
+(If we migrate to using toml config, the test reqs could be consolidated into an optional section)
+
+
+**Running tests**
+from the project root, simply run:
+
+```bash
+pytest
+# or pick a specific test file to run
+pytest tests/test_whale_viewer.py
+```
+
+To generate a coverage report to screen (also run the tests):
+```bash
+pytest --cov=src 
+```
+
+To generate reports on pass rate and coverage, to files:
+```bash
+pytest --junit-xml=test-results.xml
+pytest --cov-report=lcov --cov=src
+```
+
+
+## CI testing
+
+Initially we have an action setup that runs all tests in the `tests` directory, within the `test/tests` branch.
+
+TODO: Add some test report & coverage badges to the README.
diff --git a/pytest.ini b/pytest.ini
new file mode 100644
index 0000000..7767b6d
--- /dev/null
+++ b/pytest.ini
@@ -0,0 +1,5 @@
+[pytest]
+pythonpath = "src"
+testpaths = 
+    tests
+
diff --git a/snippets/test_upload.py b/snippets/try_upload.py
similarity index 100%
rename from snippets/test_upload.py
rename to snippets/try_upload.py
diff --git a/src/__init__.py b/src/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/apptest/demo_whale_viewer.py b/src/apptest/demo_whale_viewer.py
new file mode 100644
index 0000000..e951116
--- /dev/null
+++ b/src/apptest/demo_whale_viewer.py
@@ -0,0 +1,30 @@
+# a minimal snippet for the whale viewer, for testing purposes
+# - using AppTest to validate that the display_whale functionality
+#   is ok
+# - currently placed in the src directory (not optimal) because 
+#   I couldn't get pytest to pick it up from the tests directory. 
+#   - TODO: find a cleaner solution for organisation (maybe just config to pytest?)
+
+import streamlit as st
+
+# to run streamlit from this subdir, we need the the src dir on the path
+# NOTE: pytest doesn't need this to run the tests, but to develop the test
+# harness is hard without running streamlit 
+import sys
+from os import path
+# src (parent from here)
+src_dir = path.dirname( path.dirname( path.abspath(__file__) ) )
+sys.path.append(src_dir)
+
+
+import whale_viewer as sw_wv
+
+# a menu to pick one of the images 
+title = st.title("Whale Viewer testing")
+species = st.selectbox("Species", sw_wv.WHALE_CLASSES) 
+
+if species is not None:
+    # and display the image + reference
+    st.write(f"Selected species: {species}")
+    sw_wv.display_whale([species], 0, st)
+    
diff --git a/src/input_handling.py b/src/input_handling.py
index 2b604ed..b2631d7 100644
--- a/src/input_handling.py
+++ b/src/input_handling.py
@@ -1,3 +1,4 @@
+from fractions import Fraction
 from PIL import Image
 from PIL import ExifTags
 import re
@@ -194,14 +195,68 @@ def get_image_datetime(image_file: UploadedFile) -> str | None:
         image = Image.open(image_file)
         exif_data = image._getexif()
         if exif_data is not None:
-            for tag, value in exif_data.items():
-                if ExifTags.TAGS.get(tag) == 'DateTimeOriginal':
-                    return value
+            if ExifTags.Base.DateTimeOriginal in exif_data:
+                return exif_data.get(ExifTags.Base.DateTimeOriginal)
     except Exception as e: # FIXME: what types of exception?
          st.warning(f"Could not extract date from image metadata. (file: {image_file.name})")
          # TODO: add to logger
     return None
 
+def decimal_coords(coords:tuple, ref:str) -> Fraction:
+    """
+    Converts coordinates from degrees, minutes, and seconds to decimal degrees.
+
+    Args:
+        coords (tuple): A tuple containing three elements representing degrees, minutes, and seconds.
+        ref (str): A string representing the reference direction ('N', 'S', 'E', 'W').
+
+    Returns:
+        Fraction: The coordinates in decimal degrees. Negative if the reference is 'S' or 'W'.
+
+    Example:
+        decimal_coords((40, 26, 46), 'N') -> 40.44611111111111
+        decimal_coords((40, 26, 46), 'W') -> -40.44611111111111
+    """
+    # https://stackoverflow.com/a/73267185
+    if ref not in ['N', 'S', 'E', 'W']:
+        raise ValueError("Invalid reference direction. Must be 'N', 'S', 'E', or 'W'.")
+    if len(coords) != 3:
+        raise ValueError("Coordinates must be a tuple of three elements (degrees, minutes, seconds).")
+    
+    decimal_degrees = coords[0] + coords[1] / 60 + coords[2] / 3600
+    if ref == "S" or ref =='W':
+        decimal_degrees = -decimal_degrees
+    return decimal_degrees
+
+
+def get_image_latlon(image_file: UploadedFile) -> tuple[float, float] | None:
+    """
+    Extracts the latitude and longitude from the EXIF metadata of an uploaded image file.
+
+    Args:
+        image_file (UploadedFile): The uploaded image file from which to extract the latitude and longitude.
+
+    Returns:
+        tuple[float, float]: The latitude and longitude as a tuple if available, otherwise None.
+
+    Raises:
+        Warning: If the latitude and longitude could not be extracted from the image metadata.
+    """
+    try:
+        image = Image.open(image_file)
+        exif_data = image._getexif()
+        if exif_data is not None:
+            if ExifTags.Base.GPSInfo in exif_data:
+                gps_ifd = exif_data.get(ExifTags.Base.GPSInfo) 
+                
+                lat = float(decimal_coords(gps_ifd[ExifTags.GPS.GPSLatitude], gps_ifd[ExifTags.GPS.GPSLatitudeRef]))
+                lon = float(decimal_coords(gps_ifd[ExifTags.GPS.GPSLongitude], gps_ifd[ExifTags.GPS.GPSLongitudeRef]))
+            
+                return lat, lon
+            
+    except Exception as e: # FIXME: what types of exception?
+         st.warning(f"Could not extract latitude and longitude from image metadata. (file: {str(image_file)}")
+
 
 # an arbitrary set of defaults so testing is less painful...
 # ideally we add in some randomization to the defaults
diff --git a/tests/README.md b/tests/README.md
new file mode 100644
index 0000000..345b03b
--- /dev/null
+++ b/tests/README.md
@@ -0,0 +1,10 @@
+# Test report
+
+- overall status: ![CI test build](https://github.com/sdsc-ordes/saving-willy/actions/workflows/python-pytest.yml/badge.svg)
+- more detailed test report: TODO
+
+## Test coverage
+
+- TODO
+   - For a summary: one way is using https://github.com/GaelGirodon/ci-badges-action, can add it as a post-pytest step to the CI
+   - For a table: try this https://github.com/coroo/pytest-coverage-commentator
\ No newline at end of file
diff --git a/tests/data/cakes.jpg b/tests/data/cakes.jpg
new file mode 100644
index 0000000..ed5c25b
Binary files /dev/null and b/tests/data/cakes.jpg differ
diff --git a/tests/data/cakes_no_exif_datetime.jpg b/tests/data/cakes_no_exif_datetime.jpg
new file mode 100644
index 0000000..b881793
Binary files /dev/null and b/tests/data/cakes_no_exif_datetime.jpg differ
diff --git a/tests/data/cakes_no_exif_gps.jpg b/tests/data/cakes_no_exif_gps.jpg
new file mode 100644
index 0000000..f639dc9
Binary files /dev/null and b/tests/data/cakes_no_exif_gps.jpg differ
diff --git a/tests/requirements.txt b/tests/requirements.txt
new file mode 100644
index 0000000..f085d1d
--- /dev/null
+++ b/tests/requirements.txt
@@ -0,0 +1,6 @@
+# tests
+pytest~=8.3.4
+pytest-cov~=6.0.0
+# linting
+#flake8 
+
diff --git a/tests/test_demo_whale_viewer.py b/tests/test_demo_whale_viewer.py
new file mode 100644
index 0000000..62d43c1
--- /dev/null
+++ b/tests/test_demo_whale_viewer.py
@@ -0,0 +1,129 @@
+from streamlit.testing.v1 import AppTest
+import pytest # for the exception testing
+
+import whale_viewer as sw_wv # for data
+
+
+def test_selectbox_ok():
+    '''
+    test the snippet demoing whale viewer - relating to AppTest'able elements
+    
+    we validate that
+    - there is one selectbox present, with initial value "beluga" and index 0
+    - the two markdown elems generated dynamically by the selection corresponds
+    
+    - then changing the selection, we do the same checks again
+
+    - finally, we check there are the right number of options (26)
+    
+    '''
+    at = AppTest.from_file("src/apptest/demo_whale_viewer.py").run()
+    assert len(at.selectbox) == 1
+    assert at.selectbox[0].value == "beluga"
+    assert at.selectbox[0].index == 0
+    
+    # let's check that the markdown is right
+    # the first markdown should be "Selected species: beluga"
+    assert at.markdown[0].value == "Selected species: beluga"
+    # the second markdown should be "### :whale:  #1: Beluga"
+    print("markdown 1: ", at.markdown[1].value)
+    assert at.markdown[1].value == "### :whale:  #1: Beluga"
+
+    # now let's select a different element. index 4 is commersons_dolphin
+    v4 = "commersons_dolphin"
+    v4_str = v4.replace("_", " ").title()
+    
+    at.selectbox[0].set_value(v4).run()
+    assert at.selectbox[0].value == v4
+    assert at.selectbox[0].index == 4
+    # the first markdown should be "Selected species: commersons_dolphin"
+    assert at.markdown[0].value == f"Selected species: {v4}"
+    # the second markdown should be "### :whale:  #1: Commersons Dolphin"
+    assert at.markdown[1].value == f"### :whale:  #1: {v4_str}"
+    
+    # test there are the right number of options
+    print("PROPS=> ", dir(at.selectbox[0])) # no length unfortunately,
+    # test it dynamically intead.
+    # should be fine
+    at.selectbox[0].select_index(len(sw_wv.WHALE_CLASSES)-1).run()
+    # should fail
+    with pytest.raises(Exception):
+        at.selectbox[0].select_index(len(sw_wv.WHALE_CLASSES)).run()
+    
+def test_img_props():
+    '''
+    test the snippet demoing whale viewer - relating to the image 
+    
+    we validate that
+    - one image is displayed
+    - the caption corresponds to the data in WHALE_REFERENCES
+    - the url is a mock url
+    
+    - then changing the image, we do the same checks again
+    
+    '''
+    at = AppTest.from_file("src/apptest/demo_whale_viewer.py").run()
+    ix = 0 # we didn't interact with the dropdown, so it should be the first one
+    # could fetch the property - maybe better in case code example changes
+    ix = at.selectbox[0].index 
+    
+    elem = at.get("imgs") # hmm, apparently the naming is not consistent with the other AppTest f/w. 
+    # type(elem[0]) -> "streamlit.testing.v1.element_tree.UnknownElement" haha
+    assert len(elem) == 1 
+    img0 = elem[0]
+
+    # we can't check the image, but maybe the alt text?
+    #assert at.image[0].alt == "beluga" # no, doesn't have that property.
+
+    # for v1.39, the proto comes back something like this:
+    exp_proto = '''
+        imgs {
+        caption: "https://www.fisheries.noaa.gov/species/beluga-whale"
+        url: "/mock/media/6a21db178fcd99b82817906fc716a5c35117f4daa1d1c1d3c16ae1c8.png"
+        }
+        width: -3
+    '''
+    # from the proto string we can look for <itemtype>: "<value>" pairs and make a dictionary
+    import re
+
+    def parse_proto(proto_str):
+        pattern = r'(\w+):\s*"([^"]+)"'
+        matches = re.findall(pattern, proto_str)
+        return {key: value for key, value in matches}
+
+    parsed_proto = parse_proto(str(img0.proto))
+    # we're expecting the caption to be WHALE_REFERENCES[ix]
+    print(parsed_proto)
+    assert "caption" in parsed_proto
+    assert parsed_proto["caption"] == sw_wv.WHALE_REFERENCES[ix]
+    assert "url" in parsed_proto
+    assert parsed_proto["url"].startswith("/mock/media")
+    
+    print(sw_wv.WHALE_REFERENCES[ix])
+
+    # now let's switch to another index
+    ix = 15
+    v15 = sw_wv.WHALE_CLASSES[ix]
+    v15_str = v15.replace("_", " ").title()
+    at.selectbox[0].set_value(v15).run()
+    
+    elem = at.get("imgs") 
+    img0 = elem[0]
+    print("[INFO] image 0 after adjusting dropdown:")
+    print(img0.type, type(img0.proto))#, "\t", i0.value) # it doesn't have a value
+    print(img0.proto)
+    
+    
+    parsed_proto = parse_proto(str(img0.proto))
+    # we're expecting the caption to be WHALE_REFERENCES[ix]
+    print(parsed_proto)
+    assert "caption" in parsed_proto
+    assert parsed_proto["caption"] == sw_wv.WHALE_REFERENCES[ix]
+    assert "url" in parsed_proto
+    assert parsed_proto["url"].startswith("/mock/media")
+    
+
+
+    
+
+
diff --git a/tests/test_input_handling.py b/tests/test_input_handling.py
new file mode 100644
index 0000000..b61a318
--- /dev/null
+++ b/tests/test_input_handling.py
@@ -0,0 +1,208 @@
+import pytest
+from pathlib import Path
+
+from input_handling import is_valid_email, is_valid_number
+from input_handling import get_image_datetime, get_image_latlon, decimal_coords
+
+# generate tests for is_valid_email
+# - test with valid email
+#    - basic email with @ and .
+#    - test with email with multiple .
+# - test with empty email
+# - test with None email
+# - test with non-string email
+# - test with invalid email
+#    - test with email without @
+#    - test with email without .
+#    - test with email without domain
+#    - test with email without username
+#    - test with email without TLD
+#    - test with email with multiple @
+#    - test with email starting with the + sign
+
+
+def test_is_valid_email_valid():
+    assert is_valid_email("j@a.bc")
+    assert is_valid_email("j+oneuse@a.bc")
+    assert is_valid_email("a@b.cd")
+    assert is_valid_email("a.b@c.de")
+    assert is_valid_email("a.b@c.de.fg")
+    
+def test_is_valid_email_empty():
+    assert not is_valid_email("")
+    
+def test_is_valid_email_none():
+    with pytest.raises(TypeError):
+        is_valid_email(None)
+    
+def test_is_valid_email_non_string():
+    with pytest.raises(TypeError):
+        is_valid_email(123)
+        
+    
+def test_is_valid_email_invalid():
+    assert not is_valid_email("a.bc")
+    assert not is_valid_email("a@bc")
+    assert not is_valid_email("a.b@cc")
+    assert not is_valid_email("@b.cc")
+    assert not is_valid_email("a@.cc")
+    assert not is_valid_email("a@b.")
+    assert not is_valid_email("a@bb.")
+    assert not is_valid_email("a@b.cc.")
+    assert not is_valid_email("a@b@c.d")
+
+# not sure how xfails come through the CI pipeline yet.
+# maybe better to just comment out this stuff until pipeline is setup, then can check /extend
+@pytest.mark.xfail(reason="Bug identified, but while setting up CI having failing tests causes more headache")
+def test_is_valid_email_invalid_plus():
+    assert not is_valid_email("+@test.com")
+    assert not is_valid_email("+oneuse@test.com")
+
+
+def test_is_valid_number_valid():
+    # with a sign or without, fractional or integer are all valid
+    assert is_valid_number("123")
+    assert is_valid_number("123.456")
+    assert is_valid_number("-123")
+    assert is_valid_number("-123.456")
+    assert is_valid_number("+123")
+    assert is_valid_number("+123.456")
+
+def test_is_valid_number_empty():
+    assert not is_valid_number("")
+
+def test_is_valid_number_none():
+    with pytest.raises(TypeError):
+        is_valid_number(None)
+
+def test_is_valid_number_invalid():
+    # func should return False for strings that are not numbers
+    assert not is_valid_number("abc")
+    assert not is_valid_number("123abc")
+    assert not is_valid_number("abc123")
+    assert not is_valid_number("123.456.789")
+    assert not is_valid_number("123,456") 
+    assert not is_valid_number("123-456")
+    assert not is_valid_number("123+456")
+def test_is_valid_number_valid():
+    assert is_valid_number("123")
+    assert is_valid_number("123.456")
+    assert is_valid_number("-123")
+    assert is_valid_number("-123.456")
+    assert is_valid_number("+123")
+    assert is_valid_number("+123.456")
+
+def test_is_valid_number_empty():
+    assert not is_valid_number("")
+
+def test_is_valid_number_none():
+    with pytest.raises(TypeError):
+        is_valid_number(None)
+
+def test_is_valid_number_invalid():
+    assert not is_valid_number("abc")
+    assert not is_valid_number("123abc")
+    assert not is_valid_number("abc123")
+    assert not is_valid_number("123.456.789")
+    assert not is_valid_number("123,456")
+    assert not is_valid_number("123-456")
+    assert not is_valid_number("123+456")
+
+    
+    
+# tests for get_image_datetime
+# - testing with a valid image with complete, valid metadata
+# - testing with a valid image with incomplete metadata (missing datetime info -- that's a legitimate case we should handle)
+# - testing with a valid image with incomplete metadata (missing GPS info -- should not affect the datetime extraction)
+# - testing with a valid image with no metadata
+# - timezones too
+
+
+test_data_pth = Path('tests/data/')
+def test_get_image_datetime():
+    
+    # this image has lat, lon, and datetime
+    f1 = test_data_pth / 'cakes.jpg'
+    assert get_image_datetime(f1) == "2024:10:24 15:59:45"
+    #"+02:00"
+    # hmm, the full datetime requires timezone, which is called OffsetTimeOriginal
+    
+    # missing GPS loc: this should not interfere with the datetime
+    f2 = test_data_pth / 'cakes_no_exif_gps.jpg'
+    assert get_image_datetime(f2) == "2024:10:24 15:59:45"
+    
+    # missng datetime -> expect None
+    f3 = test_data_pth / 'cakes_no_exif_datetime.jpg'
+    assert get_image_datetime(f3) == None
+    
+
+def test_get_image_latlon():
+    # this image has lat, lon, and datetime
+    f1 = test_data_pth / 'cakes.jpg'
+    assert get_image_latlon(f1) == (46.51860277777778, 6.562075)
+    
+    # missing GPS loc
+    f2 = test_data_pth / 'cakes_no_exif_gps.jpg'
+    assert get_image_latlon(f2) == None
+    
+    # missng datetime -> expect gps not affected
+    f3 = test_data_pth / 'cakes_no_exif_datetime.jpg'
+    assert get_image_latlon(f3) == (46.51860277777778, 6.562075)
+
+# tests for get_image_latlon with empty file
+def test_get_image_latlon_empty():
+    assert get_image_latlon("") == None
+    
+# tests for decimal_coords
+# - without input, py raises TypeError 
+# - with the wrong length of input (expecting 3 elements in the tuple), expect ValueError
+# - with string inputs instead of numeric, we get a TypeError (should the func bother checking this? happens as built in)
+# - with ref direction not in ['N', 'S', 'E', 'W'], expect ValueError, try X, x, NW. 
+# - with valid inputs, expect the correct output
+
+
+# test data for decimal_coords: (deg,min,sec), ref, expected output
+coords_conversion_data = [
+    ((30, 1, 2), 'W', -30.01722222),
+    ((30, 1, 2), 'E', 30.01722222),
+    ((30, 1, 2), 'N', 30.01722222),
+    ((30, 1, 2), 'S', -30.01722222),
+    ((46, 31, 6.97), 'N', 46.51860278),
+    ((6, 33, 43.47), 'E', 6.56207500)
+]
+@pytest.mark.parametrize("input_coords, ref, expected_output", coords_conversion_data)
+def test_decimal_coords(input_coords, ref, expected_output):
+    assert decimal_coords(input_coords, ref) == pytest.approx(expected_output)
+    
+def test_decimal_coords_no_input():
+    with pytest.raises(TypeError):
+        decimal_coords()
+        
+def test_decimal_coords_wrong_length():
+    with pytest.raises(ValueError):
+        decimal_coords((1, 2), 'W')
+
+    with pytest.raises(ValueError):
+        decimal_coords((30,), 'W')
+        
+    with pytest.raises(ValueError):
+        decimal_coords((30, 1, 2, 4), 'W')
+
+def test_decimal_coords_non_numeric():
+    with pytest.raises(TypeError):
+        decimal_coords(('1', '2', '3'), 'W')
+        
+    
+def test_decimal_coords_invalid_ref():
+    with pytest.raises(ValueError):
+        decimal_coords((30, 1, 2), 'X')
+        
+    with pytest.raises(ValueError):
+        decimal_coords((30, 1, 2), 'x')
+        
+    with pytest.raises(ValueError):
+        decimal_coords((30, 1, 2), 'NW')
+        
+        
+
+
diff --git a/tests/test_whale_viewer.py b/tests/test_whale_viewer.py
new file mode 100644
index 0000000..d8df56b
--- /dev/null
+++ b/tests/test_whale_viewer.py
@@ -0,0 +1,50 @@
+import pytest
+from pathlib import Path
+
+from whale_viewer import format_whale_name
+
+# testing format_whale_name
+# - testing with valid whale names
+# - testing with invalid whale names
+# - empty string
+# - with the wrong datatype
+
+def test_format_whale_name_ok():
+    # some with 1 word, most with 2 words, others with 3 or 4.
+    assert format_whale_name("right_whale") == "Right Whale"
+    assert format_whale_name("blue_whale") == "Blue Whale"
+    assert format_whale_name("humpback_whale") == "Humpback Whale"
+    assert format_whale_name("sperm_whale") == "Sperm Whale"
+    assert format_whale_name("fin_whale") == "Fin Whale"
+    assert format_whale_name("sei_whale") == "Sei Whale"
+    assert format_whale_name("minke_whale") == "Minke Whale"
+    assert format_whale_name("gray_whale") == "Gray Whale"
+    assert format_whale_name("bowhead_whale") == "Bowhead Whale"
+    assert format_whale_name("beluga") == "Beluga"
+
+    assert format_whale_name("long_finned_pilot_whale") == "Long Finned Pilot Whale"
+    assert format_whale_name("melon_headed_whale") == "Melon Headed Whale"
+    assert format_whale_name("pantropic_spotted_dolphin") == "Pantropic Spotted Dolphin"
+    assert format_whale_name("spotted_dolphin") == "Spotted Dolphin"
+    assert format_whale_name("killer_whale") == "Killer Whale"
+
+
+def test_format_whale_name_invalid():
+    # not so clear what this would be, except perhaps a string that has gone through the fucn alrealdy?
+    assert format_whale_name("Right Whale") == "Right Whale"
+    assert format_whale_name("Blue Whale") == "Blue Whale"
+    assert format_whale_name("Long Finned Pilot Whale") == "Long Finned Pilot Whale"
+
+# testing with empty string
+def test_format_whale_name_empty():
+    assert format_whale_name("") == ""
+    
+# testing with the wrong datatype
+# we should get a TypeError - currently it fails with a AttributeError
+@pytest.mark.xfail
+def test_format_whale_name_none():
+    with pytest.raises(TypeError):
+        format_whale_name(None)
+        
+
+# display_whale requires UI to test it. 
\ No newline at end of file