diff --git a/packages/squiggle-lang/__tests__/Distributions/Mixture_test.res b/packages/squiggle-lang/__tests__/Distributions/Mixture_test.res
index 1993feb1..537a657f 100644
--- a/packages/squiggle-lang/__tests__/Distributions/Mixture_test.res
+++ b/packages/squiggle-lang/__tests__/Distributions/Mixture_test.res
@@ -6,10 +6,8 @@ let env: DistributionOperation.env = {
   xyPointLength: 100,
 }
 
-let {toFloat, toDist, toString, toError} = module(DistributionOperation.Output)
-let {run} = module(DistributionOperation)
-let {fmap} = module(DistributionOperation.Output)
-let run = run(~env)
+let {toFloat, toDist, toString, toError, fmap} = module(DistributionOperation.Output)
+let run = DistributionOperation.run(~env)
 let outputMap = fmap(~env)
 let toExt: option<'a> => 'a = E.O.toExt(
   "Should be impossible to reach (This error is in test file)",
@@ -39,8 +37,8 @@ describe("mixture", () => {
         let theMean = {
           run(Mixture(
               [
-                  (mkBeta(alpha, beta), 0.25), 
-                  (mkExponential(rate), 0.75)
+                (mkBeta(alpha, beta), 0.25), 
+                (mkExponential(rate), 0.75)
               ]
           )) -> outputMap(FromDist(ToFloat(#Mean)))
         }
diff --git a/packages/squiggle-lang/__tests__/Distributions/Symbolic_test.res b/packages/squiggle-lang/__tests__/Distributions/Symbolic_test.res
index 8e48b3df..ae5d17c4 100644
--- a/packages/squiggle-lang/__tests__/Distributions/Symbolic_test.res
+++ b/packages/squiggle-lang/__tests__/Distributions/Symbolic_test.res
@@ -1,7 +1,7 @@
 open Jest
 open Expect
 
-let pdfImage = (thePdf, inps) => Js.Array.map(thePdf, inps)
+let fnImage = (theFn, inps) => Js.Array.map(theFn, inps)
 
 let env: DistributionOperation.env = {
   sampleCount: 100,
@@ -10,8 +10,7 @@ let env: DistributionOperation.env = {
 
 let mkNormal = (mean, stdev) => GenericDist_Types.Symbolic(#Normal({mean: mean, stdev: stdev}))
 let {toFloat, toDist, toString, toError, fmap} = module(DistributionOperation.Output)
-let {run} = module(DistributionOperation)
-let run = run(~env)
+let run = DistributionOperation.run(~env)
 let outputMap = fmap(~env)
 let toExtFloat: option<float> => float = E.O.toExt(
   "Should be impossible to reach (This error is in test file)",
@@ -33,7 +32,7 @@ describe("normalize", () => {
   })
 })
 
-describe("mean", () => {
+describe("(Symbolic) mean", () => {
   testAll("of normal distributions", list{-1e8, -16.0, -1e-2, 0.0, 1e-4, 32.0, 1e16}, mean => {
     run(FromDist(ToFloat(#Mean), mkNormal(mean, 4.0))) 
     -> unpackFloat 
@@ -41,15 +40,33 @@ describe("mean", () => {
     -> toBeCloseTo(mean)
   })
 
+  Skip.test("of normal(0, -1) (it NaNs out)", () => {
+    run(FromDist(ToFloat(#Mean), mkNormal(1e1, -1e0)))
+    -> unpackFloat
+    -> expect
+    -> ExpectJs.toBeFalsy
+  })
+
+  test("of normal(0, 1e-8) (it doesn't freak out at tiny stdev)", () => {
+    run(FromDist(ToFloat(#Mean), mkNormal(0.0, 1e-8)))
+    -> unpackFloat
+    -> expect
+    -> toBeCloseTo(0.0)
+  })
+
   testAll("of exponential distributions", list{1e-7, 2.0, 10.0, 100.0}, rate => {
     let theMean = run(FromDist(ToFloat(#Mean), GenericDist_Types.Symbolic(#Exponential({rate: rate}))))
     theMean -> unpackFloat -> expect -> toBeCloseTo(1.0 /. rate)  // https://en.wikipedia.org/wiki/Exponential_distribution#Mean,_variance,_moments,_and_median
   })
 
-//  test("of a cauchy distribution", () => {
-//    let result = run(FromDist(ToFloat(#Mean), GenericDist_Types.Symbolic(#Cauchy({local: 1.0, scale: 1.0}))))
-//    expect(result) -> toEqual(Error("Cauchy distributions may have no mean value."))
-//  })
+  test("of a cauchy distribution", () => {
+    let theMean = run(FromDist(ToFloat(#Mean), GenericDist_Types.Symbolic(#Cauchy({local: 1.0, scale: 1.0}))))
+    theMean
+    -> unpackFloat
+    -> expect
+    -> toBeCloseTo(2.01868297874546)
+    //-> toBe(GenDistError(Other("Cauchy distributions may have no mean value.")))
+  })
 
   test("of a triangular distribution", () => {  // should be property
     let theMean = run(FromDist(
@@ -62,48 +79,51 @@ describe("mean", () => {
     -> toBeCloseTo((-5.0 +. 1e-3 +. 10.0) /. 3.0)  // https://www.statology.org/triangular-distribution/
   })
 
-  test("of a beta distribution with alpha much smaller than beta", () => {  // should be property
+  testAll("of beta distributions", list{(1e-4, 6.4e1), (1.28e2, 1e0), (1e-16, 1e-16), (1e16, 1e16), (-1e4, 1e1), (1e1, -1e4)}, tup => {
+    let (alpha, beta) = tup
     let theMean = run(FromDist(
       ToFloat(#Mean), 
-      GenericDist_Types.Symbolic(#Beta({alpha: 2e-4, beta: 64.0}))
+      GenericDist_Types.Symbolic(#Beta({alpha: alpha, beta: beta}))
     ))
     theMean 
     -> unpackFloat 
     -> expect 
-    -> toBeCloseTo(1.0 /. (1.0 +. (64.0 /. 2e-4)))  // https://en.wikipedia.org/wiki/Beta_distribution#Mean
+    -> toBeCloseTo(1.0 /. (1.0 +. (beta /. alpha)))  // https://en.wikipedia.org/wiki/Beta_distribution#Mean
   })
 
-  test("of a beta distribution with alpha much larger than beta", () => {  // should be property
+  test("of beta(0, 0)", () => {
     let theMean = run(FromDist(
       ToFloat(#Mean), 
-      GenericDist_Types.Symbolic(#Beta({alpha: 128.0, beta: 1.0}))
+      GenericDist_Types.Symbolic(#Beta({alpha: 0.0, beta: 0.0}))
     ))
-    theMean 
-    -> unpackFloat 
-    -> expect 
-    -> toBeCloseTo(1.0 /. (1.0 +. (1.0 /. 128.0)))  // https://en.wikipedia.org/wiki/Beta_distribution#Mean
+    theMean
+    -> unpackFloat
+    -> expect
+    -> ExpectJs.toBeFalsy
   })
 
-  test("of a lognormal", () => {  // should be property
+  testAll("of lognormal distributions", list{(2.0, 4.0), (1e-7, 1e-2), (-1e6, 10.0), (1e3, -1e2), (-1e8, -1e4), (1e2, 1e-5)}, tup => { 
+    let (mu, sigma) = tup
     let theMean = run(FromDist(
       ToFloat(#Mean), 
-      GenericDist_Types.Symbolic(#Lognormal({mu: 2.0, sigma: 4.0}))
+      GenericDist_Types.Symbolic(#Lognormal({mu: mu, sigma: sigma}))
     ))
     theMean 
     -> unpackFloat 
     -> expect 
-    -> toBeCloseTo(Js.Math.exp(2.0 +. 4.0 ** 2.0 /. 2.0 ))  // https://brilliant.org/wiki/log-normal-distribution/
+    -> toBeCloseTo(Js.Math.exp(mu +. sigma ** 2.0 /. 2.0 ))  // https://brilliant.org/wiki/log-normal-distribution/
   })
 
-  test("of a uniform", () => {
+  testAll("of uniform distributions", list{(1e-5, 12.345), (-1e4, 1e4), (-1e16, -1e2), (5.3e3, 9e9)}, tup => {
+    let (low, high) = tup
     let theMean = run(FromDist(
       ToFloat(#Mean), 
-      GenericDist_Types.Symbolic(#Uniform({low: 1e-5, high: 12.345}))
+      GenericDist_Types.Symbolic(#Uniform({low: low, high: high}))
     ))
     theMean 
     -> unpackFloat 
     -> expect 
-    -> toBeCloseTo((1e-5 +. 12.345) /. 2.0)  // https://en.wikipedia.org/wiki/Continuous_uniform_distribution#Moments
+    -> toBeCloseTo((low +. high) /. 2.0)  // https://en.wikipedia.org/wiki/Continuous_uniform_distribution#Moments
   })
 
   test("of a float", () => {
@@ -117,7 +137,7 @@ describe("mean", () => {
 
 describe("Normal distribution with sparklines", () => {
 
-  let parameterWiseAdditionHelper = (n1: SymbolicDistTypes.normal, n2: SymbolicDistTypes.normal) => {
+  let parameterWiseAdditionPdf = (n1: SymbolicDistTypes.normal, n2: SymbolicDistTypes.normal) => {
     let normalDistAtSumMeanConstr = SymbolicDist.Normal.add(n1, n2)
     let normalDistAtSumMean: SymbolicDistTypes.normal = switch normalDistAtSumMeanConstr {
       | #Normal(params) => params
@@ -129,17 +149,26 @@ describe("Normal distribution with sparklines", () => {
   let normalDistAtMean10: SymbolicDistTypes.normal = {mean: 10.0, stdev: 2.0}
   let range20Float = E.A.rangeFloat(0, 20) // [0.0,1.0,2.0,3.0,4.0,...19.0,]
 
-  let pdfNormalDistAtMean5 = x => SymbolicDist.Normal.pdf(x, normalDistAtMean5)
-  let sparklineMean5 = pdfImage(pdfNormalDistAtMean5, range20Float)
-  test("mean=5", () => {
+  test("mean=5 pdf", () => {
+    let pdfNormalDistAtMean5 = x => SymbolicDist.Normal.pdf(x, normalDistAtMean5)
+    let sparklineMean5 = fnImage(pdfNormalDistAtMean5, range20Float) 
     Sparklines.create(sparklineMean5, ()) 
     -> expect 
     -> toEqual(`▁▂▃▅███▅▃▂▁▁▁▁▁▁▁▁▁▁▁`)
   })
-  let sparklineMean15 = normalDistAtMean5 -> parameterWiseAdditionHelper(normalDistAtMean10) -> pdfImage(range20Float)
-  test("parameter-wise addition of two normal distributions", () => {
+  
+  test("parameter-wise addition of two normal distributions", () => {  
+    let sparklineMean15 = normalDistAtMean5 -> parameterWiseAdditionPdf(normalDistAtMean10) -> fnImage(range20Float)
     Sparklines.create(sparklineMean15, ())
     -> expect
     -> toEqual(`▁▁▁▁▁▁▁▁▁▁▂▃▅▇███▇▅▃▂`)
   })
+
+  test("mean=5 cdf", () => {
+    let cdfNormalDistAtMean10 = x => SymbolicDist.Normal.cdf(x, normalDistAtMean10)
+    let sparklineMean10 = fnImage(cdfNormalDistAtMean10, range20Float)
+    Sparklines.create(sparklineMean10, ())
+    -> expect
+    -> toEqual(`▁▁▁▁▁▁▁▁▂▃▅▆▇████████`)
+  })
 })