Two types of Test cases are there:
1) Positive Test Cases
2) Negative Test Cases

A) Positive Test Cases are:
1. Installation Testing
2.UI Testing: or Design based Testing
3. Usability testing
4. Integration Testing
5. Functional Testing
6.Non Functional Testing
7. Performance and Stress Testing
8. Reliability testing
Let’s explain one by one:
1. Installation Testing:
1) Check if the all parts of the Pan is fitting properly and no loose fitting.
2) Check if the Pan refill is fitted properly.
3) Verify the type of Pen- whether it is gel Pen or Ball Pen
2. UI Testing: or Design-based Testing:
1) We will check the design of the pen is as per required specification(given in SRS)
2) We will check the colour of the pen is as per required specification(given in SRS)
3) We will check the refill of the Pen is as per the required specification (refill Size and refill length)
4) We will check the length, breadth and width of the Pen is as per required specification(given in SRS)
5) We will check the body of the Pen- it should be metallic, plastic or any other material as per specification(given in SRS)
6) We will check that the Company LOGO is properly printed on Pen or not as per the design specification
7) Verify the company name or logo of the maker is at desired place on pen.
8) Check the tip dimension(0.5mm or 0.7mm as requested) of the pen is as per the specification or not.
9) Verify the weight of the Pen
10) Check if the enough distance present between Pen tip and pen grip Section
11) Check if the body of the Pen can be bend(up to a limit) or not, check if its material is brittle
12) We will check that pen has rubber grip or not
13) Check the pen grip Section, it must be very gentle(soft) to avoid the pressure on fingers
14) Check that the pen is with a cap or without the cap
15) Check that a clip is available on pen or on Pen cap to hang the pen on pent or shirt.
3. Usability testing :
1) Check if Pen is writing with minimum noise and vibration means the pen is smooth or not
2) Check if Pen is not making spots when it’s in the movement.
3) Check if Pen is usable for similar refill of different brands.
4. Integration Testing:
1) Check the length of the Pen body and refill.
2) Verify that refill properly fit with Pen or not
3) Verify that the Pen can be fit properly with pen cap.
5. Functional Testing :
1) Check out that pen is able to write on Paper or not
2) Check out that pen is able to write on rough surface or not
3) Check out that pen is able to write on wet paper or not
4) Check out that pen is able to write on hand or not
5) Write on paper and check out the color of ink must be same as specified
6. Non Functional Testing:
1) The look and feel of Pen must be like pen
2) The body of the pen must not be too thin or too thick
3) The look and feel must be good
4) Check out that is there any mark on pen that tells that you can write up to this limit(How many words)
7. Performance and Stress Testing:
1) Check out the condition of ink after long period of time is as per specification or not means there will be no effect of time on ink of the pen
2) Check out that how pen behave in different work conditions
3) Verify the Pen’s condition when continuously writing for very large duration
4) Check out that how pen works on different pen positions(like horizontal, vertical, above and below from head)
5) Checkout the effect of water and oil and other liquid on the text written by pen
6) Checkout that the text written by pen must not get faded after a certain time(not before specified time)
7) Check out that the text written by pen is erasable or not
8. Reliability testing:
1) Check out the minimum and maximum speed of Pen by which the user can write when writing on paper
2) Check if the material used for Pen refill and check if it’s not getting out from pen when it is in motion.
B) Negative Test Cases
1) Check out that Pen is working without refill.
2) Check out the Pen have right color ink
3) Checkout the Pen stress testing by dropping Pen down from desired height and check if nothing is breaking, no damage to Pen and Pen is working without any issues.
4) Check how Pen is working at different climate environmental conditions like at room temperature.