From 48ce8d78c4ef237928a435ef891ae068cbe45e68 Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 10:18:44 +0000
Subject: [PATCH 01/12] pass all the tests for calculateMedian function

---
 Sprint-1/fix/median.js | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index 5c5b796e1..3adc95936 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,9 +6,23 @@
 // or contains values that aren't numbers (the function is expected to throw - see the tests).
 
 function calculateMedian(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+  if (list.length === 0) {
+    throw new Error("calculateMedian requires a non-empty array");
+  }
+  for (const item of list) {
+    if (typeof item !== "number") {
+      throw new Error("calculateMedian requires an array of numbers");
+    }
+  }
   const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  const sorted = [...list].sort((a, b) => a - b);
+  if (sorted.length % 2 === 0) {
+    return (sorted[middleIndex - 1] + sorted[middleIndex]) / 2;
+  }
+  return sorted[middleIndex];
 }
 
 module.exports = calculateMedian;

From 2b6e82254d0aa68fd92fad4b38be50399cae70bf Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 11:02:57 +0000
Subject: [PATCH 02/12] make the function throw an error if the input is not an
 array of numbers

---
 Sprint-1/implement/max.js | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 6dd76378e..a061a69fa 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,4 +1,15 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+  if (!elements.every((v) => typeof v === "number" && !Number.isNaN(v))) {
+    throw new Error("findMax requires an array of numbers");
+  }
+  let max = -Infinity;
+  for (const value of elements) {
+    if (value > max) max = value;
+  }
+  return max;
 }
 
 module.exports = findMax;

From 8ccb8b0fedcc687232bc766d3091ffb6a966e24b Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 11:03:24 +0000
Subject: [PATCH 03/12] create the test edges and all the test case passed

---
 Sprint-1/implement/max.test.js | 82 +++++++++++++++++++++++-----------
 1 file changed, 57 insertions(+), 25 deletions(-)

diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index ff3fbb5e5..f525f2ba5 100644
--- a/Sprint-1/implement/max.test.js
+++ b/Sprint-1/implement/max.test.js
@@ -11,33 +11,65 @@ We have set things up already so that this file can see your function from the o
 */
 
 const findMax = require("./max.js");
+describe("findMax", () => {
+  // Given an empty array
+  // When passed to the max function
+  // Then it should return -Infinity
+  // Delete this test.todo and replace it with a test.
+  it("returns -Infinity for []", () => {
+    expect(findMax([])).toEqual(-Infinity);
+  });
 
-// Given an empty array
-// When passed to the max function
-// Then it should return -Infinity
-// Delete this test.todo and replace it with a test.
-test.todo("given an empty array, returns -Infinity");
+  // Given an array with one number
+  // When passed to the max function
+  // Then it should return that number
+  it("returns the only number for [1]", () => {
+    expect(findMax([1])).toEqual(1);
+  });
 
-// Given an array with one number
-// When passed to the max function
-// Then it should return that number
+  // Given an array with both positive and negative numbers
+  // When passed to the max function
+  // Then it should return the largest number overall
+  it("returns the largest of positive and negative numbers", () => {
+    expect(findMax([5, -7, 3, -5])).toEqual(5);
+  });
 
-// Given an array with both positive and negative numbers
-// When passed to the max function
-// Then it should return the largest number overall
+  // Given an array with just negative numbers
+  // When passed to the max function
+  // Then it should return the closest one to zero
+  it("returns the negative number closest to zero", () => {
+    expect(findMax([-10, -3, -20, -5])).toEqual(-3);
+  });
 
-// Given an array with just negative numbers
-// When passed to the max function
-// Then it should return the closest one to zero
+  // Given an array with decimal numbers
+  // When passed to the max function
+  // Then it should return the largest decimal number
+  it("returns the largest decimal number", () => {
+    expect(findMax([1.5, 2.25, 2.2, -0.5])).toEqual(2.25);
+  });
+  // Given an array containing a value that isn't a number
+  // When passed to the max function
+  // Then it should throw Error("findMax requires an array of numbers")
+  it("throws when the array contains a non-number", () => {
+    expect(() => findMax(["hey", 10, "hi", 60, 10])).toThrow(
+      new Error("findMax requires an array of numbers")
+    );
+  });
+  // Given something that isn't an array at all, such as "hey", 42 or no argument
+  // When passed to the max function
+  // Then it should throw Error("findMax requires an array of numbers")
+  it.each([["hey"], [42], [null], [{}]])(
+    "throws when given %p instead of an array",
+    (input) => {
+      expect(() => findMax(input)).toThrow(
+        new Error("findMax requires an array of numbers")
+      );
+    }
+  );
 
-// Given an array with decimal numbers
-// When passed to the max function
-// Then it should return the largest decimal number
-
-// Given an array containing a value that isn't a number
-// When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
-
-// Given something that isn't an array at all, such as "hey", 42 or no argument
-// When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
+  it("throws when called with no argument", () => {
+    expect(() => findMax()).toThrow(
+      new Error("findMax requires an array of numbers")
+    );
+  });
+});

From 381ec0d53f9162246822c1b7937313e61676e44b Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 11:20:07 +0000
Subject: [PATCH 04/12] create a function to sum an array of numbers with input
 validation

---
 Sprint-1/implement/sum.js | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 9062aafe3..7a49fd1f6 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,4 +1,15 @@
 function sum(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("sum requires an array of numbers");
+  }
+  if (!elements.every((a) => typeof a === "number" && !Number.isNaN(a))) {
+    throw new Error("sum requires an array of numbers");
+  }
+  let Total = 0;
+  for (const value of elements) {
+    Total += value;
+  }
+  return Total;
 }
 
 module.exports = sum;

From 1e00cf05a43333f10f500e4d4629ab5eee092954 Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 11:20:21 +0000
Subject: [PATCH 05/12] all tests for sum function with various inputs and edge
 cases

---
 Sprint-1/implement/sum.test.js | 77 +++++++++++++++++++++++-----------
 1 file changed, 52 insertions(+), 25 deletions(-)

diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index a288e0f0a..6c0cc307e 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -9,28 +9,55 @@ E.g. sum(['hey', 10, 'hi', 60, 10]) throws Error("sum requires an array of numbe
 const sum = require("./sum.js");
 
 // Acceptance Criteria:
-
-// Given an empty array
-// When passed to the sum function
-// Then it should return 0
-test.todo("given an empty array, returns 0")
-
-// Given an array with just one number
-// When passed to the sum function
-// Then it should return that number
-
-// Given an array containing negative numbers
-// When passed to the sum function
-// Then it should still return the correct total sum
-
-// Given an array with decimal/float numbers
-// When passed to the sum function
-// Then it should return the correct total sum
-
-// Given an array containing a value that isn't a number
-// When passed to the sum function
-// Then it should throw Error("sum requires an array of numbers")
-
-// Given something that isn't an array at all, such as "hey", 42 or no argument
-// When passed to the sum function
-// Then it should throw Error("sum requires an array of numbers")
+describe("findMax", () => {
+  // Given an empty array
+  // When passed to the sum function
+  // Then it should return 0
+  it("returns 0 for []", () => {
+    expect(sum([])).toEqual(0);
+  });
+
+  // Given an array with just one number
+  // When passed to the sum function
+  // Then it should return that number
+  it("returns the sum of number for [7]", () => {
+    expect(sum([7])).toEqual(7);
+  });
+  // Given an array containing negative numbers
+  // When passed to the sum function
+  // Then it should still return the correct total sum
+  it("returns the correct sum with negative numbers", () => {
+    expect(sum([10, -4, -8, 5])).toEqual(3);
+  });
+  // Given an array with decimal/float numbers
+  // When passed to the sum function
+  // Then it should return the correct total sum
+  it("returns the correct sum with decimal numbers", () => {
+    expect(sum([1.5, 2.25, 0.25])).toBeCloseTo(4);
+    expect(sum([0.1, 0.2])).toBeCloseTo(0.3);
+  });
+
+  // Given an array containing a value that isn't a number
+  // When passed to the sum function
+  // Then it should throw Error("sum requires an array of numbers")
+  it("throws when the array contains a non-number", () => {
+    expect(() => sum(["hey", 10, "hi", 60, 10])).toThrow(
+      new Error("sum requires an array of numbers")
+    );
+  });
+  // Given something that isn't an array at all, such as "hey", 42 or no argument
+  // When passed to the sum function
+  // Then it should throw Error("sum requires an array of numbers")
+  it.each([["hey"], [42], [null], [{}]])(
+    "throws when given %p instead of an array",
+    (input) => {
+      expect(() => sum(input)).toThrow(
+        new Error("sum requires an array of numbers")
+      );
+    }
+  );
+
+  it("throws when called with no argument", () => {
+    expect(() => sum()).toThrow(new Error("sum requires an array of numbers"));
+  });
+});

From c85bbffaf12407aadf1146bf25e39a5888f5914f Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 11:26:52 +0000
Subject: [PATCH 06/12] correct the small typo in the test description for sum
 function

---
 Sprint-1/implement/sum.test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index 6c0cc307e..fff315115 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -9,7 +9,7 @@ E.g. sum(['hey', 10, 'hi', 60, 10]) throws Error("sum requires an array of numbe
 const sum = require("./sum.js");
 
 // Acceptance Criteria:
-describe("findMax", () => {
+describe("sum", () => {
   // Given an empty array
   // When passed to the sum function
   // Then it should return 0

From 533cce3a37d31902473a071726257247eb696938 Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 11:41:16 +0000
Subject: [PATCH 07/12] write the code for the dedupe function.

---
 Sprint-1/implement/dedupe.js | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 781e8718a..b54117bd9 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1 +1,11 @@
-function dedupe() {}
+function dedupe(list) {
+  const result = [];
+  for (const item of list) {
+    if (!result.includes(item)) {
+      result.push(item);
+    }
+  }
+  return result;
+}
+
+module.exports = dedupe;

From 8b0d12902170232af93a291d4aaf4e488bf48e79 Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 11:41:33 +0000
Subject: [PATCH 08/12] make all the edges cases and acceptance criteria for
 the dedupe function

---
 Sprint-1/implement/dedupe.test.js | 45 +++++++++++++++++++++++--------
 1 file changed, 34 insertions(+), 11 deletions(-)

diff --git a/Sprint-1/implement/dedupe.test.js b/Sprint-1/implement/dedupe.test.js
index d7c8e3d8e..3cef7e23e 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -12,17 +12,40 @@ E.g. dedupe([1, 2, 1]) returns [1, 2]
 */
 
 // Acceptance Criteria:
+describe("dedupe", () => {
+  // Given an empty array
+  // When passed to the dedupe function
+  // Then it should return an empty array
+  it("returns [] for []", () => {
+    expect(dedupe([])).toEqual([]);
+  });
 
-// Given an empty array
-// When passed to the dedupe function
-// Then it should return an empty array
-test.todo("given an empty array, it returns an empty array");
+  // Given an array with no duplicates
+  // When passed to the dedupe function
+  // Then it should return a copy of the original array
+  it("returns a copy of the array when there are no duplicates", () => {
+    // const list = [1, 2, 3];
+    // const result = dedupe(list);
+    // expect(result).toEqual([1, 2, 3]);
+    // expect(result).not.toBe(list);
+    expect(dedupe([1, "1", 2])).toEqual([1, "1", 2]);
+  });
+  // Given an array of strings or numbers
+  // When passed to the dedupe function
+  // Then it should return a new array with duplicates removed while preserving the
+  // first occurrence of each element from the original array.
+  it("removes duplicate numbers, keeping the first occurrence order", () => {
+    expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+    expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+  });
 
-// Given an array with no duplicates
-// When passed to the dedupe function
-// Then it should return a copy of the original array
+  it("treats 1 and '1' as different values", () => {
+    expect(dedupe([1, "1", 1, "1"])).toEqual([1, "1"]);
+  });
 
-// Given an array of strings or numbers
-// When passed to the dedupe function
-// Then it should return a new array with duplicates removed while preserving the 
-// first occurrence of each element from the original array.
+  it("doesn't modify the input array", () => {
+    const list = [1, 1, 2];
+    dedupe(list);
+    expect(list).toEqual([1, 1, 2]);
+  });
+});

From a77f4b8d1954b20a632722f02113f70644238780 Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 11:59:41 +0000
Subject: [PATCH 09/12] make a mean function that calculates the mean of an
 array of numbers

---
 Sprint-1/implement/mean.js | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/Sprint-1/implement/mean.js b/Sprint-1/implement/mean.js
index 36909ea1f..c7748da1d 100644
--- a/Sprint-1/implement/mean.js
+++ b/Sprint-1/implement/mean.js
@@ -1,3 +1,21 @@
-function calculateMean(list) {}
+function calculateMean(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+
+  if (list.length === 0) {
+    throw new Error("calculateMean requires a non-empty array");
+  }
+
+  if (!list.every((v) => typeof v === "number" && !Number.isNaN(v))) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+
+  let total = 0;
+  for (const value of list) {
+    total += value;
+  }
+  return total / list.length;
+}
 
 module.exports = calculateMean;

From 43846933dd4dd328482fd02116f43eae6c4120bc Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 12:00:08 +0000
Subject: [PATCH 10/12] make all the edges cases for the calculateMean function

---
 Sprint-1/implement/mean.test.js | 89 ++++++++++++++++++++++-----------
 1 file changed, 60 insertions(+), 29 deletions(-)

diff --git a/Sprint-1/implement/mean.test.js b/Sprint-1/implement/mean.test.js
index 847b88676..cf1656b72 100644
--- a/Sprint-1/implement/mean.test.js
+++ b/Sprint-1/implement/mean.test.js
@@ -18,33 +18,64 @@ We have set things up already so that this file can see your function from the o
 const calculateMean = require("./mean.js");
 
 // Acceptance criteria:
+describe("calculatedMean", () => {
+  // Given an array of numbers
+  // When passed to calculateMean
+  // Then it should return their mean
+  // Delete this test.todo and replace it with a test.
+  it("returns 3 for [1, 2, 6]", () => {
+    expect(calculateMean([1, 2, 6])).toEqual(3);
+  });
 
-// Given an array of numbers
-// When passed to calculateMean
-// Then it should return their mean
-// Delete this test.todo and replace it with a test.
-test.todo("given [1, 2, 6], returns 3");
-
-// Given an array with a single number
-// When passed to calculateMean
-// Then it should return that number
-
-// Given an array containing negative or decimal numbers
-// When passed to calculateMean
-// Then it should return the correct mean
-
-// Given an empty array
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires a non-empty array")
-
-// Given a value that isn't an array, e.g. "banana", 42, null or {}
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
-
-// Given no argument at all
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
-
-// Given an array containing a non-number value, e.g. [1, "2", 3]
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
+  // Given an array with a single number
+  // When passed to calculateMean
+  // Then it should return that number
+  it("returns the number itself for [7]", () => {
+    expect(calculateMean([7])).toEqual(7);
+  });
+  // Given an array containing negative or decimal numbers
+  // When passed to calculateMean
+  // Then it should return the correct mean
+  it("returns the correct mean with negative numbers", () => {
+    expect(calculateMean([-2, 4, -6, 8])).toEqual(1);
+  });
+  it("returns the correct mean with decimal numbers", () => {
+    expect(calculateMean([1.5, 2.5, 3.5])).toBeCloseTo(2.5);
+    expect(calculateMean([0.1, 0.2])).toBeCloseTo(0.15);
+  });
+  // Given an empty array
+  // When passed to calculateMean
+  // Then it should throw Error("calculateMean requires a non-empty array")
+  it("throws when given an empty array", () => {
+    expect(() => calculateMean([])).toThrow(
+      new Error("calculateMean requires a non-empty array")
+    );
+  });
+  // Given a value that isn't an array, e.g. "banana", 42, null or {}
+  // When passed to calculateMean
+  // Then it should throw Error("calculateMean requires an array of numbers")
+  it.each([["banana"], [42], [null], [{}]])(
+    "throws when given %p instead of an array",
+    (input) => {
+      expect(() => calculateMean(input)).toThrow(
+        new Error("calculateMean requires an array of numbers")
+      );
+    }
+  );
+  // Given no argument at all
+  // When passed to calculateMean
+  // Then it should throw Error("calculateMean requires an array of numbers")
+  it("throws when called with no argument", () => {
+    expect(() => calculateMean()).toThrow(
+      new Error("calculateMean requires an array of numbers")
+    );
+  });
+  // Given an array containing a non-number value, e.g. [1, "2", 3]
+  // When passed to calculateMean
+  // Then it should throw Error("calculateMean requires an array of numbers")
+  it("throws when the array contains a non-number", () => {
+    expect(() => calculateMean([1, "2", 3])).toThrow(
+      new Error("calculateMean requires an array of numbers")
+    );
+  });
+});

From c6c2e2f04b620de161de7c0c57f1e310b68127a2 Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 12:11:30 +0000
Subject: [PATCH 11/12] in describeMedian function i add the try catch block to
 handle errors when calculating the median

---
 Sprint-1/implement/describe-median.js | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/Sprint-1/implement/describe-median.js b/Sprint-1/implement/describe-median.js
index 3381cfc0a..f6fdd5660 100644
--- a/Sprint-1/implement/describe-median.js
+++ b/Sprint-1/implement/describe-median.js
@@ -20,6 +20,13 @@ function calculateMedian(list) {
 }
 
 // Implement this function. See describe-median.test.js for the acceptance criteria.
-function describeMedian(list) {}
+function describeMedian(list) {
+  try {
+    const median = calculateMedian(list);
+    return `The median is ${median}`;
+  } catch (error) {
+    return `Could not calculate a median: ${error.message}`;
+  }
+}
 
 module.exports = describeMedian;

From d139abcefebb167f8f8ead5d234273b6fa40d3b0 Mon Sep 17 00:00:00 2001
From: gaireprakash20-ops <gaireprakash20@gmail.com>
Date: Thu, 5 Nov 2026 12:12:06 +0000
Subject: [PATCH 12/12] MAKE A text edges that can be used to describe the
 median of a list of numbers

---
 Sprint-1/implement/describe-median.test.js | 65 ++++++++++++++++++----
 1 file changed, 54 insertions(+), 11 deletions(-)

diff --git a/Sprint-1/implement/describe-median.test.js b/Sprint-1/implement/describe-median.test.js
index e7d18a264..7aaf09ba4 100644
--- a/Sprint-1/implement/describe-median.test.js
+++ b/Sprint-1/implement/describe-median.test.js
@@ -16,17 +16,60 @@ message, so the caller can see what went wrong.
 const describeMedian = require("./describe-median.js");
 
 // Acceptance criteria:
+describe("describeMedian", () => {
+  // Given an array of numbers
+  // When passed to describeMedian
+  // Then it should return "The median is " followed by the median
+  // Delete this test.todo and replace it with a test.
+  it('returns "The median is 2" for [1, 2, 3]', () => {
+    expect(describeMedian([1, 2, 3])).toEqual("The median is 2");
+  });
 
-// Given an array of numbers
-// When passed to describeMedian
-// Then it should return "The median is " followed by the median
-// Delete this test.todo and replace it with a test.
-test.todo('given [1, 2, 3], returns "The median is 2"');
+  it("works for an even-length array", () => {
+    expect(describeMedian([1, 2, 3, 4])).toEqual("The median is 2.5");
+  });
 
-// Given an empty array
-// When passed to describeMedian
-// Then it should return "Could not calculate a median: calculateMedian requires a non-empty array"
+  it("works for an unsorted array", () => {
+    expect(describeMedian([3, 1, 2])).toEqual("The median is 2");
+  });
 
-// Given something that isn't an array of numbers, e.g. "banana"
-// When passed to describeMedian
-// Then it should return "Could not calculate a median: calculateMedian requires an array of numbers"
+  // Given an empty array
+  // When passed to describeMedian
+  // Then it should return "Could not calculate a median: calculateMedian requires a non-empty array"
+  it("explains the problem for an empty array", () => {
+    expect(describeMedian([])).toEqual(
+      "Could not calculate a median: calculateMedian requires a non-empty array"
+    );
+  });
+
+  // Given something that isn't an array of numbers, e.g. "banana"
+  // When passed to describeMedian
+  // Then it should return "Could not calculate a median: calculateMedian requires an array of numbers"
+  it("explains the problem for an empty array", () => {
+    expect(describeMedian([])).toEqual(
+      "Could not calculate a median: calculateMedian requires a non-empty array"
+    );
+  });
+
+  // Given something that isn't an array of numbers, explain why
+  it.each([["banana"], [42], [null], [{}]])(
+    "explains the problem when given %p instead of an array",
+    (input) => {
+      expect(describeMedian(input)).toEqual(
+        "Could not calculate a median: calculateMedian requires an array of numbers"
+      );
+    }
+  );
+
+  it("explains the problem when called with no argument", () => {
+    expect(describeMedian()).toEqual(
+      "Could not calculate a median: calculateMedian requires an array of numbers"
+    );
+  });
+
+  it("explains the problem for an array containing a non-number", () => {
+    expect(describeMedian([1, "2", 3])).toEqual(
+      "Could not calculate a median: calculateMedian requires an array of numbers"
+    );
+  });
+});