diff --git a/.gitignore b/.gitignore
index e6e7241..ca8abf8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,3 +20,5 @@
 .DS_Store
 
 /.ignore/
+
+/coverage/
diff --git a/package.json b/package.json
index 1913a03..7c16cdc 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,8 @@
   "scripts": {
     "dev": "node esbuild.config.mjs",
     "build": "tsc -noEmit -skipLibCheck && node esbuild.config.mjs production",
-    "export-schema": "typescript-json-schema --required --strictNullChecks --validationKeywords --ignoreErrors --refs --id https://raw.githubusercontent.com/BambusControl/obsidian-unicode-search/0.5.0-NEXT/resources/save-data-schema.json --out ./resources/save-data-schema.json tsconfig.json SaveData"
+    "export-schema": "typescript-json-schema --required --strictNullChecks --validationKeywords --ignoreErrors --refs --id https://raw.githubusercontent.com/BambusControl/obsidian-unicode-search/0.5.0-NEXT/resources/save-data-schema.json --out ./resources/save-data-schema.json tsconfig.json SaveData",
+    "test": "jest"
   },
   "keywords": [
     "obsidian"
diff --git a/src/libraries/comparison/compare-usage-tracked.characters.spec.ts b/src/libraries/comparison/compare-usage-tracked.characters.spec.ts
new file mode 100644
index 0000000..5ef128d
--- /dev/null
+++ b/src/libraries/comparison/compare-usage-tracked.characters.spec.ts
@@ -0,0 +1,31 @@
+import {compareUsageTrackedCharacters} from "./compare-usage-tracked.characters";
+
+test(
+	"later use is before sooner use",
+	() => {
+		expect(compareUsageTrackedCharacters(
+			{
+				lastUsed: 1,
+				useCount: 1,
+			},
+			{
+				lastUsed: 0,
+				useCount: 1,
+			}
+		)).toBe(-1)
+	}
+)
+
+test(
+	"one use is before zero uses",
+	() => {
+		expect(compareUsageTrackedCharacters(
+			{
+				useCount: 1,
+			},
+			{
+				useCount: 0,
+			}
+		)).toBe(-1)
+	}
+)
diff --git a/src/libraries/comparison/compare-stat-tracked.characters.ts b/src/libraries/comparison/compare-usage-tracked.characters.ts
similarity index 86%
rename from src/libraries/comparison/compare-stat-tracked.characters.ts
rename to src/libraries/comparison/compare-usage-tracked.characters.ts
index 6b23dfd..a2b77af 100644
--- a/src/libraries/comparison/compare-stat-tracked.characters.ts
+++ b/src/libraries/comparison/compare-usage-tracked.characters.ts
@@ -4,7 +4,7 @@ import {inverse} from "../order/inverse";
 import {compareNullable} from "./compare.nullable";
 import {compareNumbers} from "./compare.numbers";
 
-export function compareStatTrackedCharacters(left: UsageInfo, right: UsageInfo): Order {
+export function compareUsageTrackedCharacters(left: UsageInfo, right: UsageInfo): Order {
 	// We want the most recently used to be first.
 	const lastUsedComparison = compareNullable(
 		left.lastUsed,
diff --git a/src/libraries/comparison/compare.characters.spec.ts b/src/libraries/comparison/compare.characters.spec.ts
new file mode 100644
index 0000000..cd1627c
--- /dev/null
+++ b/src/libraries/comparison/compare.characters.spec.ts
@@ -0,0 +1,55 @@
+import {compareCharacters} from "./compare.characters";
+
+test(
+    "character with name `a` is before character with name `b`",
+    () => {
+        expect(compareCharacters(
+            {
+                char: " ",
+                name: "a"
+            },
+            {
+                char: " ",
+                name: "b"
+            }
+        )).toBe(-1)
+    }
+)
+
+test(
+    "character with `use` is before character without",
+    () => {
+        expect(compareCharacters(
+            {
+                char: " ",
+                name: "b",
+				lastUsed: 1,
+				useCount: 1
+            },
+            {
+                char: " ",
+                name: "a",
+            }
+        )).toBe(-1)
+    }
+)
+
+test(
+    "characters with same `name` and `use` are equal",
+    () => {
+        expect(compareCharacters(
+            {
+                char: " ",
+                name: "name",
+				lastUsed: 1,
+				useCount: 1
+            },
+            {
+                char: " ",
+                name: "name",
+				lastUsed: 1,
+				useCount: 1
+            }
+        )).toBe(0)
+    }
+)
diff --git a/src/libraries/comparison/compare.characters.ts b/src/libraries/comparison/compare.characters.ts
index a0f467f..b29e925 100644
--- a/src/libraries/comparison/compare.characters.ts
+++ b/src/libraries/comparison/compare.characters.ts
@@ -1,7 +1,7 @@
 import {Order} from "../order/order";
 import {UsageInfo} from "../types/usage-info";
 import {compareNullable} from "./compare.nullable";
-import {compareStatTrackedCharacters} from "./compare-stat-tracked.characters";
+import {compareUsageTrackedCharacters} from "./compare-usage-tracked.characters";
 import {compareUnicodeNames} from "./compare-unicode.names";
 import {Character} from "../types/character";
 
@@ -9,7 +9,7 @@ export function compareCharacters(left: Character, right: Character): Order {
 	const order = compareNullable(
 		left as UsageInfo,
 		right as UsageInfo,
-		(l, r) => compareStatTrackedCharacters(l, r),
+		(l, r) => compareUsageTrackedCharacters(l, r),
 	);
 
 	if (order != Order.Equal) {
diff --git a/src/libraries/comparison/compare.nullable.spec.ts b/src/libraries/comparison/compare.nullable.spec.ts
new file mode 100644
index 0000000..ef0073e
--- /dev/null
+++ b/src/libraries/comparison/compare.nullable.spec.ts
@@ -0,0 +1,24 @@
+import {expect, test} from "@jest/globals";
+import {compareNullable} from "./compare.nullable";
+import {compareNumbers} from "./compare.numbers";
+
+test(
+    "null equals null",
+    () => {
+       expect(compareNullable(null, null, compareNumbers)).toBe(0);
+    }
+)
+
+test(
+    "non-null is less than null",
+    () => {
+       expect(compareNullable(0, null, compareNumbers)).toBe(-1);
+    }
+)
+
+test(
+    "null is more than non-null",
+    () => {
+       expect(compareNullable(null, 0, compareNumbers)).toBe(1);
+    }
+)
diff --git a/src/libraries/comparison/compare.numbers.spec.ts b/src/libraries/comparison/compare.numbers.spec.ts
new file mode 100644
index 0000000..a1c42dd
--- /dev/null
+++ b/src/libraries/comparison/compare.numbers.spec.ts
@@ -0,0 +1,23 @@
+import {expect, test} from "@jest/globals";
+import {compareNumbers} from "./compare.numbers";
+
+test(
+    "one equals one",
+    () => {
+       expect(compareNumbers(1, 1)).toBe(0);
+    }
+)
+
+test(
+    "zero is less than one",
+    () => {
+       expect(compareNumbers(0, 1)).toBe(-1);
+    }
+)
+
+test(
+    "two is more than one",
+    () => {
+       expect(compareNumbers(2, 1)).toBe(1);
+    }
+)
diff --git a/src/libraries/helpers/hexadecimal.characters.spec.ts b/src/libraries/helpers/hexadecimal.characters.spec.ts
new file mode 100644
index 0000000..7ada635
--- /dev/null
+++ b/src/libraries/helpers/hexadecimal.characters.spec.ts
@@ -0,0 +1,11 @@
+import {toHexadecimal} from "./hexadecimal.characters";
+
+test(
+    "character `b` is `0062`",
+    () => {
+        expect(toHexadecimal({
+            "char": "b",
+            "name": "latin small letter b"
+        })).toBe("0062")
+    }
+)