diff --git a/.changeset/gentle-dingos-explain.md b/.changeset/gentle-dingos-explain.md
new file mode 100644
index 0000000000..0f58873351
--- /dev/null
+++ b/.changeset/gentle-dingos-explain.md
@@ -0,0 +1,5 @@
+---
+"@khanacademy/kas": patch
+---
+
+Add some tests for mixed numbers in KAS.
diff --git a/packages/kas/src/__tests__/evaluating.test.ts b/packages/kas/src/__tests__/evaluating.test.ts
index 099ee575ce..207ada0d60 100644
--- a/packages/kas/src/__tests__/evaluating.test.ts
+++ b/packages/kas/src/__tests__/evaluating.test.ts
@@ -13,11 +13,16 @@ expect.extend({
         vars: Variables = {},
         functions?: ReadonlyArray<string>,
     ) {
-        const actual = KAS.parse(input, {functions: functions}).expr.eval(
-            vars,
-            {functions: functions},
-        );
+        const parsed = KAS.parse(input, {functions: functions});
+        if (parsed.false || parsed.error) {
+            return {
+                pass: false,
+                message: () =>
+                    `unable to parse: ${input} (error: ${parsed.error})`,
+            };
+        }
 
+        const actual = parsed.expr.eval(vars, {functions: functions});
         if (actual !== expected) {
             return {
                 pass: false,
@@ -96,4 +101,40 @@ describe("evaluating", () => {
         expect("f(x-1)-f(x)").toEvaluateAs(-7, {f: "x^3", x: 2}, ["f"]);
         expect("g(1)").toEvaluateAs(-1, {f: "x", g: "-f(x)"}, ["f", "g"]);
     });
+
+    // TODO (LEMS-2198): these are tests from a failed attempt
+    // to support mixed numbers correctly. Keeping so we have a record
+    // of what's wrong and what's expected.
+    test("fraction expressions", () => {
+        // wrong
+        expect("2\\frac{1}{2} + 1").toEvaluateAs(2);
+        // correct
+        // expect("2\\frac{1}{2} + 1").toEvaluateAs(3.5);
+
+        // wrong
+        expect("(2\\frac{1}{2}) + 1").toEvaluateAs(2);
+        // correct
+        // expect("(2\\frac{1}{2}) + 1").toEvaluateAs(3.5);
+
+        // wrong
+        expect("-2\\frac{1}{2} + 1").toEvaluateAs(0);
+        // correct
+        // expect("-2\\frac{1}{2} + 1").toEvaluateAs(-1.5);
+
+        // wrong
+        expect("(-2\\frac{1}{2}) + 1").toEvaluateAs(0);
+        // correct
+        // expect("(-2\\frac{1}{2}) + 1").toEvaluateAs(-1.5);
+
+        // should continue to pass after LEMS-2198 is done
+        expect("2-\\frac{1}{2} + 1").toEvaluateAs(2.5);
+        expect("(2-\\frac{1}{2}) + 1").toEvaluateAs(2.5);
+        expect("(2)\\frac{1}{2} + 1").toEvaluateAs(2);
+        expect("2(\\frac{1}{2}) + 1").toEvaluateAs(2);
+        expect("\\frac{1}{2}2 + 1").toEvaluateAs(2);
+        expect("2 + \\frac{1}{2} + 1").toEvaluateAs(3.5);
+        expect("2 * \\frac{1}{2}").toEvaluateAs(1);
+        expect("2 2").toEvaluateAs(4);
+        expect("2\\pi").toEvaluateAs(6.283185307179586);
+    });
 });
diff --git a/packages/kas/src/__tests__/parsing.test.ts b/packages/kas/src/__tests__/parsing.test.ts
index b59e1f4c36..6753d6e885 100644
--- a/packages/kas/src/__tests__/parsing.test.ts
+++ b/packages/kas/src/__tests__/parsing.test.ts
@@ -13,7 +13,8 @@ expect.extend({
         if (actual !== expected) {
             return {
                 pass: false,
-                message: () => `${input} parses as ${expected}`,
+                message: () =>
+                    `input: ${input}\nexpected:${expected}\nactual: ${actual}`,
             };
         }
 
@@ -113,6 +114,8 @@ describe("parsing", () => {
         expect("\\frac{42}{1}").toParseAs("42/1");
         expect("\\frac{0}{42}").toParseAs("0/42");
 
+        // TODO (LEMS-2198): this should actually be:
+        // expect("2\\frac{1}{2}").toParseAs("2+1/2");
         expect("2\\frac{1}{2}").toParseAs("2*1/2");
         expect("\\frac{1}{2}\\frac{1}{2}").toParseAs("1/2*1/2");
         expect("-\\frac{1}{2}").toParseAs("-1/2");
@@ -128,6 +131,8 @@ describe("parsing", () => {
         expect("\\dfrac{42}{1}").toParseAs("42/1");
         expect("\\dfrac{0}{42}").toParseAs("0/42");
 
+        // TODO (LEMS-2198): this should actually be:
+        // expect("2\\dfrac{1}{2}").toParseAs("2+1/2");
         expect("2\\dfrac{1}{2}").toParseAs("2*1/2");
         expect("\\dfrac{1}{2}\\dfrac{1}{2}").toParseAs("1/2*1/2");
         expect("-\\dfrac{1}{2}").toParseAs("-1/2");